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Presidential Pardon



Sort list of array linked objects by keys and values



The 2019 Stack Overflow Developer Survey Results Are In
Announcing the arrival of Valued Associate #679: Cesar Manara
Planned maintenance scheduled April 17/18, 2019 at 00:00UTC (8:00pm US/Eastern)Functional Knapsack Problem in PythonSorting movie search results by similaritySorting a list and another list inside each itemGeneric natural merge sort a linked-list in CIce Cream ParlorFlight combinations between two citiesCompute the minimum distance between two points in a 2-D planeConvert a JS DataTable to an array of objectsSorting a 2-dimensional array with counting sortRemove nth node from last position in linked list



.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty margin-bottom:0;








3












$begingroup$


I have this sample data:



let trips = [

from: "DEN",
to: "JFK"
,

from: "SEA",
to: "DEN"
,

from: 'JFK',
to: 'SEA'
,
];


and my origin is 'JFK', I want to sort the list by how I have traveled. So for instance, this should be the end result:



let trips = [

from: 'JFK',
to: 'SEA'
,

from: "SEA",
to: "DEN"
,

from: "DEN",
to: "JFK"
,
];


My solution works but it's not very well written, but I tried!



function sortByLinked(trips, origin = 'JFK') 
let sortedArray = [];

let first = trips.filter(trip => trip.from === origin)[0];
sortedArray.push(first);

for(var i = 0; i < trips.length; i++)
if(sortedArray[0].to === trips[i].from)
sortedArray.push(trips[i]);



for(var i = 0; i < trips.length; i++)
if(sortedArray[1].to === trips[i].from)
sortedArray.push(trips[i]);



return sortedArray;


sortByLinked(trips)









share|improve this question











$endgroup$



migrated from stackoverflow.com 5 hours ago


This question came from our site for professional and enthusiast programmers.

















  • $begingroup$
    is it like the origin and final destination always the same? and how many intermediate trips are going to be present?
    $endgroup$
    – karthick
    5 hours ago










  • $begingroup$
    Is from unique for all elements?
    $endgroup$
    – Taplar
    5 hours ago










  • $begingroup$
    @karthick yes the origin and final should be the same.
    $endgroup$
    – Shivam Bhalla
    5 hours ago










  • $begingroup$
    @Taplar yes from is unique
    $endgroup$
    – Shivam Bhalla
    5 hours ago










  • $begingroup$
    The task you want to perform is a simple kind of topological sorting.
    $endgroup$
    – 200_success
    3 hours ago

















3












$begingroup$


I have this sample data:



let trips = [

from: "DEN",
to: "JFK"
,

from: "SEA",
to: "DEN"
,

from: 'JFK',
to: 'SEA'
,
];


and my origin is 'JFK', I want to sort the list by how I have traveled. So for instance, this should be the end result:



let trips = [

from: 'JFK',
to: 'SEA'
,

from: "SEA",
to: "DEN"
,

from: "DEN",
to: "JFK"
,
];


My solution works but it's not very well written, but I tried!



function sortByLinked(trips, origin = 'JFK') 
let sortedArray = [];

let first = trips.filter(trip => trip.from === origin)[0];
sortedArray.push(first);

for(var i = 0; i < trips.length; i++)
if(sortedArray[0].to === trips[i].from)
sortedArray.push(trips[i]);



for(var i = 0; i < trips.length; i++)
if(sortedArray[1].to === trips[i].from)
sortedArray.push(trips[i]);



return sortedArray;


sortByLinked(trips)









share|improve this question











$endgroup$



migrated from stackoverflow.com 5 hours ago


This question came from our site for professional and enthusiast programmers.

















  • $begingroup$
    is it like the origin and final destination always the same? and how many intermediate trips are going to be present?
    $endgroup$
    – karthick
    5 hours ago










  • $begingroup$
    Is from unique for all elements?
    $endgroup$
    – Taplar
    5 hours ago










  • $begingroup$
    @karthick yes the origin and final should be the same.
    $endgroup$
    – Shivam Bhalla
    5 hours ago










  • $begingroup$
    @Taplar yes from is unique
    $endgroup$
    – Shivam Bhalla
    5 hours ago










  • $begingroup$
    The task you want to perform is a simple kind of topological sorting.
    $endgroup$
    – 200_success
    3 hours ago













3












3








3





$begingroup$


I have this sample data:



let trips = [

from: "DEN",
to: "JFK"
,

from: "SEA",
to: "DEN"
,

from: 'JFK',
to: 'SEA'
,
];


and my origin is 'JFK', I want to sort the list by how I have traveled. So for instance, this should be the end result:



let trips = [

from: 'JFK',
to: 'SEA'
,

from: "SEA",
to: "DEN"
,

from: "DEN",
to: "JFK"
,
];


My solution works but it's not very well written, but I tried!



function sortByLinked(trips, origin = 'JFK') 
let sortedArray = [];

let first = trips.filter(trip => trip.from === origin)[0];
sortedArray.push(first);

for(var i = 0; i < trips.length; i++)
if(sortedArray[0].to === trips[i].from)
sortedArray.push(trips[i]);



for(var i = 0; i < trips.length; i++)
if(sortedArray[1].to === trips[i].from)
sortedArray.push(trips[i]);



return sortedArray;


sortByLinked(trips)









share|improve this question











$endgroup$




I have this sample data:



let trips = [

from: "DEN",
to: "JFK"
,

from: "SEA",
to: "DEN"
,

from: 'JFK',
to: 'SEA'
,
];


and my origin is 'JFK', I want to sort the list by how I have traveled. So for instance, this should be the end result:



let trips = [

from: 'JFK',
to: 'SEA'
,

from: "SEA",
to: "DEN"
,

from: "DEN",
to: "JFK"
,
];


My solution works but it's not very well written, but I tried!



function sortByLinked(trips, origin = 'JFK') 
let sortedArray = [];

let first = trips.filter(trip => trip.from === origin)[0];
sortedArray.push(first);

for(var i = 0; i < trips.length; i++)
if(sortedArray[0].to === trips[i].from)
sortedArray.push(trips[i]);



for(var i = 0; i < trips.length; i++)
if(sortedArray[1].to === trips[i].from)
sortedArray.push(trips[i]);



return sortedArray;


sortByLinked(trips)






javascript algorithm sorting graph






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited 3 hours ago









200_success

131k17157422




131k17157422










asked 5 hours ago









Shivam BhallaShivam Bhalla

1875




1875




migrated from stackoverflow.com 5 hours ago


This question came from our site for professional and enthusiast programmers.









migrated from stackoverflow.com 5 hours ago


This question came from our site for professional and enthusiast programmers.













  • $begingroup$
    is it like the origin and final destination always the same? and how many intermediate trips are going to be present?
    $endgroup$
    – karthick
    5 hours ago










  • $begingroup$
    Is from unique for all elements?
    $endgroup$
    – Taplar
    5 hours ago










  • $begingroup$
    @karthick yes the origin and final should be the same.
    $endgroup$
    – Shivam Bhalla
    5 hours ago










  • $begingroup$
    @Taplar yes from is unique
    $endgroup$
    – Shivam Bhalla
    5 hours ago










  • $begingroup$
    The task you want to perform is a simple kind of topological sorting.
    $endgroup$
    – 200_success
    3 hours ago
















  • $begingroup$
    is it like the origin and final destination always the same? and how many intermediate trips are going to be present?
    $endgroup$
    – karthick
    5 hours ago










  • $begingroup$
    Is from unique for all elements?
    $endgroup$
    – Taplar
    5 hours ago










  • $begingroup$
    @karthick yes the origin and final should be the same.
    $endgroup$
    – Shivam Bhalla
    5 hours ago










  • $begingroup$
    @Taplar yes from is unique
    $endgroup$
    – Shivam Bhalla
    5 hours ago










  • $begingroup$
    The task you want to perform is a simple kind of topological sorting.
    $endgroup$
    – 200_success
    3 hours ago















$begingroup$
is it like the origin and final destination always the same? and how many intermediate trips are going to be present?
$endgroup$
– karthick
5 hours ago




$begingroup$
is it like the origin and final destination always the same? and how many intermediate trips are going to be present?
$endgroup$
– karthick
5 hours ago












$begingroup$
Is from unique for all elements?
$endgroup$
– Taplar
5 hours ago




$begingroup$
Is from unique for all elements?
$endgroup$
– Taplar
5 hours ago












$begingroup$
@karthick yes the origin and final should be the same.
$endgroup$
– Shivam Bhalla
5 hours ago




$begingroup$
@karthick yes the origin and final should be the same.
$endgroup$
– Shivam Bhalla
5 hours ago












$begingroup$
@Taplar yes from is unique
$endgroup$
– Shivam Bhalla
5 hours ago




$begingroup$
@Taplar yes from is unique
$endgroup$
– Shivam Bhalla
5 hours ago












$begingroup$
The task you want to perform is a simple kind of topological sorting.
$endgroup$
– 200_success
3 hours ago




$begingroup$
The task you want to perform is a simple kind of topological sorting.
$endgroup$
– 200_success
3 hours ago










3 Answers
3






active

oldest

votes


















4












$begingroup$

Your solution only works if there's exactly 3 trips. After you find the first trip, put it at the front of the array and then find each subsequent one but instead of using a for loop like you're doing there are other ways to find the next trip like using Array.map() or Array.filter().



Here's one way to sort it in place and can handle any number of trips greater than 1.






function sortByLinked(trips, origin = 'JFK') 

// this will be useful
function swap(array, index1, index2)
let temp = array[index1];
array[index1] = array[index2];
array[index2] = temp;


// find first one
let first = trips.filter(trip => trip.from === origin)[0];

// put him in the front of the list
swap(trips, trips.map(trip => trip.from).indexOf(first.from), 0);

// sort it in place
for(let i=1; i<trips.length; i++)
swap(trips, i, trips.map(trip => trip.from).indexOf(trips[i-1].to));









share|improve this answer










New contributor




matthewlam.js is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.






$endgroup$












  • $begingroup$
    Because ecmascript-6 is used here: "Two variables values can be swapped in one destructuring expression."
    $endgroup$
    – Sᴀᴍ Onᴇᴌᴀ
    5 hours ago



















2












$begingroup$

Code style



  • Use constants for variables that do not change. Eg const sortedArray = [];


  • Don't include the type in the name, Eg const sortedArray = []; can be Eg const sorted = [];



  • The default parameter in this case seams inappropriate as it is likely that "JFK" is not an origin in all calls to this function. If no origin is given one could assume that the first item in trips contains the origin. function sortByLinked(trips, origin = trips[0].from) { which will throw an error if trips is empty so the function should not be called with an empty trips array if you don't pass the from parameter.



    However in this example best to leave the default as undefined if not passed as that will return an empty array which is more fitting the input parameters.



  • The name sort is inappropriate as in JS it implies that the array be sorted in place, that all items be sorted (may not be possible).


  • You have declared i two times. As a var you should put the declaration at the top of the function and not in the for loop.


  • Rather than use Array.filter you can use Array.find. It will find the first instance.


  • Using for...of rather than for(;;) reduces the code complexity.


  • No point continuing the search inside the for loops when you have found a match. Use the break token to stop a loop early


  • Put a space between if and (


  • Don't forget to add the ; where appropriate. It is missing from the call sortByLinked(trips)


  • You call the origin origin and from this can get confusing. Keep the naming unambiguous. As the trip items use from then that would be the better name for the second input argument.


Using the above points to modify your code we get



function tripFrom(trips, from) 
const sorted = [];
const first = trips.find(trip => trip.from === from);
sorted.push(first);

for (const trip of trips)
if (first.to === trip.from)
sorted.push(trip);
break;


for (const trip of trips)
if (sorted[sorted.length - 1].to === trip.from)
sorted.push(trips);
break;


return sorted;


sortByLinked(trips, "JFK");


This is still not a good solution. Its not at all DRY (don't repeat yourself) and is hard coded to a single use case.



Improving the function.



It can all be done within a single loop and work for any length array.



To create the function we must add some constraints on the array trips and what to do when we encounter any problems.



  1. That the array trips contains objects that each have the property from and to that are correctly formatted static strings. The resulting array is erroneous or indeterminate if not so.

  2. That the array does not contain circular trips shorter than the array length.

  3. That a complete trip length is no longer than the array, or when a matching trip.to can not be found. The returned array can be 0 to trips.length in size.

  4. Locations are case sensitive.

  5. If there is more than one matching trip.from it is assumed that the first match in trips is the correct one. (It would be interesting to extract the longest possible trip from? or the shortest trip that returns to the origin?)

Example



function tripFrom(trips, from) 
const result = [];
while (result.length < trips.length)
const trip = trips.find(trip => trip.from === from);
if (!trip) break
from = trip.to;
result.push(trip);

return result;

tripFrom(trips, "JFK");


Or if it is known that the trip is the same length as the input array.



function tripFrom(trips, from) 
const res = [];
while (res.length < trips.length)
from = (res[res.length] = trips.find(trip => trip.from === from)).to;

return res;

tripFrom(trips, "JFK");


It is unclear if you want the array sorted in place. If that is a requirement then the above version can be modified to do that by simply copying the results array res to the trips array. You can empty an array by setting its length to zero. The spread ... operator in this case spreads the array items over the functions arguments trips.push(...res) thus pushing all the items to the array.



function tripFrom(trips, from) 
const res = [];
while (res.length < trips.length)
from = (res[res.length] = trips.find(trip => trip.from === from)).to;

trips.length = 0;
trips.push(...res);
return trips;

tripFrom(trips, "JFK");





share|improve this answer









$endgroup$




















    1












    $begingroup$

    It would be good if your function could work for more than 3 trips.



    And for larger chains of trips it becomes important to make it efficient. It is not efficient to search for the next trip by scanning the whole array. This will make the solution have O(n²) time complexity. So I would suggest creating a Map first, so that you can access a trip by its from property in constant time:






    function sortByLinked(trips, origin = "JFK") 
    const map = new Map(trips.map(trip => [trip.from, trip]));
    const result = [];
    for (let trip; trip = map.get(origin); origin = trip.to)
    result.push(trip);
    map.delete(origin);

    return result;


    const trips = [from: "DEN",to: "JFK",from: "SEA",to: "DEN",from: 'JFK', to: 'SEA'];
    const sorted = sortByLinked(trips, "JFK");
    console.log(sorted);








    share|improve this answer









    $endgroup$













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      3 Answers
      3






      active

      oldest

      votes








      3 Answers
      3






      active

      oldest

      votes









      active

      oldest

      votes






      active

      oldest

      votes









      4












      $begingroup$

      Your solution only works if there's exactly 3 trips. After you find the first trip, put it at the front of the array and then find each subsequent one but instead of using a for loop like you're doing there are other ways to find the next trip like using Array.map() or Array.filter().



      Here's one way to sort it in place and can handle any number of trips greater than 1.






      function sortByLinked(trips, origin = 'JFK') 

      // this will be useful
      function swap(array, index1, index2)
      let temp = array[index1];
      array[index1] = array[index2];
      array[index2] = temp;


      // find first one
      let first = trips.filter(trip => trip.from === origin)[0];

      // put him in the front of the list
      swap(trips, trips.map(trip => trip.from).indexOf(first.from), 0);

      // sort it in place
      for(let i=1; i<trips.length; i++)
      swap(trips, i, trips.map(trip => trip.from).indexOf(trips[i-1].to));









      share|improve this answer










      New contributor




      matthewlam.js is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.






      $endgroup$












      • $begingroup$
        Because ecmascript-6 is used here: "Two variables values can be swapped in one destructuring expression."
        $endgroup$
        – Sᴀᴍ Onᴇᴌᴀ
        5 hours ago
















      4












      $begingroup$

      Your solution only works if there's exactly 3 trips. After you find the first trip, put it at the front of the array and then find each subsequent one but instead of using a for loop like you're doing there are other ways to find the next trip like using Array.map() or Array.filter().



      Here's one way to sort it in place and can handle any number of trips greater than 1.






      function sortByLinked(trips, origin = 'JFK') 

      // this will be useful
      function swap(array, index1, index2)
      let temp = array[index1];
      array[index1] = array[index2];
      array[index2] = temp;


      // find first one
      let first = trips.filter(trip => trip.from === origin)[0];

      // put him in the front of the list
      swap(trips, trips.map(trip => trip.from).indexOf(first.from), 0);

      // sort it in place
      for(let i=1; i<trips.length; i++)
      swap(trips, i, trips.map(trip => trip.from).indexOf(trips[i-1].to));









      share|improve this answer










      New contributor




      matthewlam.js is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.






      $endgroup$












      • $begingroup$
        Because ecmascript-6 is used here: "Two variables values can be swapped in one destructuring expression."
        $endgroup$
        – Sᴀᴍ Onᴇᴌᴀ
        5 hours ago














      4












      4








      4





      $begingroup$

      Your solution only works if there's exactly 3 trips. After you find the first trip, put it at the front of the array and then find each subsequent one but instead of using a for loop like you're doing there are other ways to find the next trip like using Array.map() or Array.filter().



      Here's one way to sort it in place and can handle any number of trips greater than 1.






      function sortByLinked(trips, origin = 'JFK') 

      // this will be useful
      function swap(array, index1, index2)
      let temp = array[index1];
      array[index1] = array[index2];
      array[index2] = temp;


      // find first one
      let first = trips.filter(trip => trip.from === origin)[0];

      // put him in the front of the list
      swap(trips, trips.map(trip => trip.from).indexOf(first.from), 0);

      // sort it in place
      for(let i=1; i<trips.length; i++)
      swap(trips, i, trips.map(trip => trip.from).indexOf(trips[i-1].to));









      share|improve this answer










      New contributor




      matthewlam.js is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.






      $endgroup$



      Your solution only works if there's exactly 3 trips. After you find the first trip, put it at the front of the array and then find each subsequent one but instead of using a for loop like you're doing there are other ways to find the next trip like using Array.map() or Array.filter().



      Here's one way to sort it in place and can handle any number of trips greater than 1.






      function sortByLinked(trips, origin = 'JFK') 

      // this will be useful
      function swap(array, index1, index2)
      let temp = array[index1];
      array[index1] = array[index2];
      array[index2] = temp;


      // find first one
      let first = trips.filter(trip => trip.from === origin)[0];

      // put him in the front of the list
      swap(trips, trips.map(trip => trip.from).indexOf(first.from), 0);

      // sort it in place
      for(let i=1; i<trips.length; i++)
      swap(trips, i, trips.map(trip => trip.from).indexOf(trips[i-1].to));









      function sortByLinked(trips, origin = 'JFK') 

      // this will be useful
      function swap(array, index1, index2)
      let temp = array[index1];
      array[index1] = array[index2];
      array[index2] = temp;


      // find first one
      let first = trips.filter(trip => trip.from === origin)[0];

      // put him in the front of the list
      swap(trips, trips.map(trip => trip.from).indexOf(first.from), 0);

      // sort it in place
      for(let i=1; i<trips.length; i++)
      swap(trips, i, trips.map(trip => trip.from).indexOf(trips[i-1].to));






      function sortByLinked(trips, origin = 'JFK') 

      // this will be useful
      function swap(array, index1, index2)
      let temp = array[index1];
      array[index1] = array[index2];
      array[index2] = temp;


      // find first one
      let first = trips.filter(trip => trip.from === origin)[0];

      // put him in the front of the list
      swap(trips, trips.map(trip => trip.from).indexOf(first.from), 0);

      // sort it in place
      for(let i=1; i<trips.length; i++)
      swap(trips, i, trips.map(trip => trip.from).indexOf(trips[i-1].to));







      share|improve this answer










      New contributor




      matthewlam.js is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.









      share|improve this answer



      share|improve this answer








      edited 5 hours ago









      Sᴀᴍ Onᴇᴌᴀ

      10.3k62168




      10.3k62168






      New contributor




      matthewlam.js is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.









      answered 5 hours ago









      matthewlam.jsmatthewlam.js

      411




      411




      New contributor




      matthewlam.js is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.





      New contributor





      matthewlam.js is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.






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      Check out our Code of Conduct.











      • $begingroup$
        Because ecmascript-6 is used here: "Two variables values can be swapped in one destructuring expression."
        $endgroup$
        – Sᴀᴍ Onᴇᴌᴀ
        5 hours ago

















      • $begingroup$
        Because ecmascript-6 is used here: "Two variables values can be swapped in one destructuring expression."
        $endgroup$
        – Sᴀᴍ Onᴇᴌᴀ
        5 hours ago
















      $begingroup$
      Because ecmascript-6 is used here: "Two variables values can be swapped in one destructuring expression."
      $endgroup$
      – Sᴀᴍ Onᴇᴌᴀ
      5 hours ago





      $begingroup$
      Because ecmascript-6 is used here: "Two variables values can be swapped in one destructuring expression."
      $endgroup$
      – Sᴀᴍ Onᴇᴌᴀ
      5 hours ago














      2












      $begingroup$

      Code style



      • Use constants for variables that do not change. Eg const sortedArray = [];


      • Don't include the type in the name, Eg const sortedArray = []; can be Eg const sorted = [];



      • The default parameter in this case seams inappropriate as it is likely that "JFK" is not an origin in all calls to this function. If no origin is given one could assume that the first item in trips contains the origin. function sortByLinked(trips, origin = trips[0].from) { which will throw an error if trips is empty so the function should not be called with an empty trips array if you don't pass the from parameter.



        However in this example best to leave the default as undefined if not passed as that will return an empty array which is more fitting the input parameters.



      • The name sort is inappropriate as in JS it implies that the array be sorted in place, that all items be sorted (may not be possible).


      • You have declared i two times. As a var you should put the declaration at the top of the function and not in the for loop.


      • Rather than use Array.filter you can use Array.find. It will find the first instance.


      • Using for...of rather than for(;;) reduces the code complexity.


      • No point continuing the search inside the for loops when you have found a match. Use the break token to stop a loop early


      • Put a space between if and (


      • Don't forget to add the ; where appropriate. It is missing from the call sortByLinked(trips)


      • You call the origin origin and from this can get confusing. Keep the naming unambiguous. As the trip items use from then that would be the better name for the second input argument.


      Using the above points to modify your code we get



      function tripFrom(trips, from) 
      const sorted = [];
      const first = trips.find(trip => trip.from === from);
      sorted.push(first);

      for (const trip of trips)
      if (first.to === trip.from)
      sorted.push(trip);
      break;


      for (const trip of trips)
      if (sorted[sorted.length - 1].to === trip.from)
      sorted.push(trips);
      break;


      return sorted;


      sortByLinked(trips, "JFK");


      This is still not a good solution. Its not at all DRY (don't repeat yourself) and is hard coded to a single use case.



      Improving the function.



      It can all be done within a single loop and work for any length array.



      To create the function we must add some constraints on the array trips and what to do when we encounter any problems.



      1. That the array trips contains objects that each have the property from and to that are correctly formatted static strings. The resulting array is erroneous or indeterminate if not so.

      2. That the array does not contain circular trips shorter than the array length.

      3. That a complete trip length is no longer than the array, or when a matching trip.to can not be found. The returned array can be 0 to trips.length in size.

      4. Locations are case sensitive.

      5. If there is more than one matching trip.from it is assumed that the first match in trips is the correct one. (It would be interesting to extract the longest possible trip from? or the shortest trip that returns to the origin?)

      Example



      function tripFrom(trips, from) 
      const result = [];
      while (result.length < trips.length)
      const trip = trips.find(trip => trip.from === from);
      if (!trip) break
      from = trip.to;
      result.push(trip);

      return result;

      tripFrom(trips, "JFK");


      Or if it is known that the trip is the same length as the input array.



      function tripFrom(trips, from) 
      const res = [];
      while (res.length < trips.length)
      from = (res[res.length] = trips.find(trip => trip.from === from)).to;

      return res;

      tripFrom(trips, "JFK");


      It is unclear if you want the array sorted in place. If that is a requirement then the above version can be modified to do that by simply copying the results array res to the trips array. You can empty an array by setting its length to zero. The spread ... operator in this case spreads the array items over the functions arguments trips.push(...res) thus pushing all the items to the array.



      function tripFrom(trips, from) 
      const res = [];
      while (res.length < trips.length)
      from = (res[res.length] = trips.find(trip => trip.from === from)).to;

      trips.length = 0;
      trips.push(...res);
      return trips;

      tripFrom(trips, "JFK");





      share|improve this answer









      $endgroup$

















        2












        $begingroup$

        Code style



        • Use constants for variables that do not change. Eg const sortedArray = [];


        • Don't include the type in the name, Eg const sortedArray = []; can be Eg const sorted = [];



        • The default parameter in this case seams inappropriate as it is likely that "JFK" is not an origin in all calls to this function. If no origin is given one could assume that the first item in trips contains the origin. function sortByLinked(trips, origin = trips[0].from) { which will throw an error if trips is empty so the function should not be called with an empty trips array if you don't pass the from parameter.



          However in this example best to leave the default as undefined if not passed as that will return an empty array which is more fitting the input parameters.



        • The name sort is inappropriate as in JS it implies that the array be sorted in place, that all items be sorted (may not be possible).


        • You have declared i two times. As a var you should put the declaration at the top of the function and not in the for loop.


        • Rather than use Array.filter you can use Array.find. It will find the first instance.


        • Using for...of rather than for(;;) reduces the code complexity.


        • No point continuing the search inside the for loops when you have found a match. Use the break token to stop a loop early


        • Put a space between if and (


        • Don't forget to add the ; where appropriate. It is missing from the call sortByLinked(trips)


        • You call the origin origin and from this can get confusing. Keep the naming unambiguous. As the trip items use from then that would be the better name for the second input argument.


        Using the above points to modify your code we get



        function tripFrom(trips, from) 
        const sorted = [];
        const first = trips.find(trip => trip.from === from);
        sorted.push(first);

        for (const trip of trips)
        if (first.to === trip.from)
        sorted.push(trip);
        break;


        for (const trip of trips)
        if (sorted[sorted.length - 1].to === trip.from)
        sorted.push(trips);
        break;


        return sorted;


        sortByLinked(trips, "JFK");


        This is still not a good solution. Its not at all DRY (don't repeat yourself) and is hard coded to a single use case.



        Improving the function.



        It can all be done within a single loop and work for any length array.



        To create the function we must add some constraints on the array trips and what to do when we encounter any problems.



        1. That the array trips contains objects that each have the property from and to that are correctly formatted static strings. The resulting array is erroneous or indeterminate if not so.

        2. That the array does not contain circular trips shorter than the array length.

        3. That a complete trip length is no longer than the array, or when a matching trip.to can not be found. The returned array can be 0 to trips.length in size.

        4. Locations are case sensitive.

        5. If there is more than one matching trip.from it is assumed that the first match in trips is the correct one. (It would be interesting to extract the longest possible trip from? or the shortest trip that returns to the origin?)

        Example



        function tripFrom(trips, from) 
        const result = [];
        while (result.length < trips.length)
        const trip = trips.find(trip => trip.from === from);
        if (!trip) break
        from = trip.to;
        result.push(trip);

        return result;

        tripFrom(trips, "JFK");


        Or if it is known that the trip is the same length as the input array.



        function tripFrom(trips, from) 
        const res = [];
        while (res.length < trips.length)
        from = (res[res.length] = trips.find(trip => trip.from === from)).to;

        return res;

        tripFrom(trips, "JFK");


        It is unclear if you want the array sorted in place. If that is a requirement then the above version can be modified to do that by simply copying the results array res to the trips array. You can empty an array by setting its length to zero. The spread ... operator in this case spreads the array items over the functions arguments trips.push(...res) thus pushing all the items to the array.



        function tripFrom(trips, from) 
        const res = [];
        while (res.length < trips.length)
        from = (res[res.length] = trips.find(trip => trip.from === from)).to;

        trips.length = 0;
        trips.push(...res);
        return trips;

        tripFrom(trips, "JFK");





        share|improve this answer









        $endgroup$















          2












          2








          2





          $begingroup$

          Code style



          • Use constants for variables that do not change. Eg const sortedArray = [];


          • Don't include the type in the name, Eg const sortedArray = []; can be Eg const sorted = [];



          • The default parameter in this case seams inappropriate as it is likely that "JFK" is not an origin in all calls to this function. If no origin is given one could assume that the first item in trips contains the origin. function sortByLinked(trips, origin = trips[0].from) { which will throw an error if trips is empty so the function should not be called with an empty trips array if you don't pass the from parameter.



            However in this example best to leave the default as undefined if not passed as that will return an empty array which is more fitting the input parameters.



          • The name sort is inappropriate as in JS it implies that the array be sorted in place, that all items be sorted (may not be possible).


          • You have declared i two times. As a var you should put the declaration at the top of the function and not in the for loop.


          • Rather than use Array.filter you can use Array.find. It will find the first instance.


          • Using for...of rather than for(;;) reduces the code complexity.


          • No point continuing the search inside the for loops when you have found a match. Use the break token to stop a loop early


          • Put a space between if and (


          • Don't forget to add the ; where appropriate. It is missing from the call sortByLinked(trips)


          • You call the origin origin and from this can get confusing. Keep the naming unambiguous. As the trip items use from then that would be the better name for the second input argument.


          Using the above points to modify your code we get



          function tripFrom(trips, from) 
          const sorted = [];
          const first = trips.find(trip => trip.from === from);
          sorted.push(first);

          for (const trip of trips)
          if (first.to === trip.from)
          sorted.push(trip);
          break;


          for (const trip of trips)
          if (sorted[sorted.length - 1].to === trip.from)
          sorted.push(trips);
          break;


          return sorted;


          sortByLinked(trips, "JFK");


          This is still not a good solution. Its not at all DRY (don't repeat yourself) and is hard coded to a single use case.



          Improving the function.



          It can all be done within a single loop and work for any length array.



          To create the function we must add some constraints on the array trips and what to do when we encounter any problems.



          1. That the array trips contains objects that each have the property from and to that are correctly formatted static strings. The resulting array is erroneous or indeterminate if not so.

          2. That the array does not contain circular trips shorter than the array length.

          3. That a complete trip length is no longer than the array, or when a matching trip.to can not be found. The returned array can be 0 to trips.length in size.

          4. Locations are case sensitive.

          5. If there is more than one matching trip.from it is assumed that the first match in trips is the correct one. (It would be interesting to extract the longest possible trip from? or the shortest trip that returns to the origin?)

          Example



          function tripFrom(trips, from) 
          const result = [];
          while (result.length < trips.length)
          const trip = trips.find(trip => trip.from === from);
          if (!trip) break
          from = trip.to;
          result.push(trip);

          return result;

          tripFrom(trips, "JFK");


          Or if it is known that the trip is the same length as the input array.



          function tripFrom(trips, from) 
          const res = [];
          while (res.length < trips.length)
          from = (res[res.length] = trips.find(trip => trip.from === from)).to;

          return res;

          tripFrom(trips, "JFK");


          It is unclear if you want the array sorted in place. If that is a requirement then the above version can be modified to do that by simply copying the results array res to the trips array. You can empty an array by setting its length to zero. The spread ... operator in this case spreads the array items over the functions arguments trips.push(...res) thus pushing all the items to the array.



          function tripFrom(trips, from) 
          const res = [];
          while (res.length < trips.length)
          from = (res[res.length] = trips.find(trip => trip.from === from)).to;

          trips.length = 0;
          trips.push(...res);
          return trips;

          tripFrom(trips, "JFK");





          share|improve this answer









          $endgroup$



          Code style



          • Use constants for variables that do not change. Eg const sortedArray = [];


          • Don't include the type in the name, Eg const sortedArray = []; can be Eg const sorted = [];



          • The default parameter in this case seams inappropriate as it is likely that "JFK" is not an origin in all calls to this function. If no origin is given one could assume that the first item in trips contains the origin. function sortByLinked(trips, origin = trips[0].from) { which will throw an error if trips is empty so the function should not be called with an empty trips array if you don't pass the from parameter.



            However in this example best to leave the default as undefined if not passed as that will return an empty array which is more fitting the input parameters.



          • The name sort is inappropriate as in JS it implies that the array be sorted in place, that all items be sorted (may not be possible).


          • You have declared i two times. As a var you should put the declaration at the top of the function and not in the for loop.


          • Rather than use Array.filter you can use Array.find. It will find the first instance.


          • Using for...of rather than for(;;) reduces the code complexity.


          • No point continuing the search inside the for loops when you have found a match. Use the break token to stop a loop early


          • Put a space between if and (


          • Don't forget to add the ; where appropriate. It is missing from the call sortByLinked(trips)


          • You call the origin origin and from this can get confusing. Keep the naming unambiguous. As the trip items use from then that would be the better name for the second input argument.


          Using the above points to modify your code we get



          function tripFrom(trips, from) 
          const sorted = [];
          const first = trips.find(trip => trip.from === from);
          sorted.push(first);

          for (const trip of trips)
          if (first.to === trip.from)
          sorted.push(trip);
          break;


          for (const trip of trips)
          if (sorted[sorted.length - 1].to === trip.from)
          sorted.push(trips);
          break;


          return sorted;


          sortByLinked(trips, "JFK");


          This is still not a good solution. Its not at all DRY (don't repeat yourself) and is hard coded to a single use case.



          Improving the function.



          It can all be done within a single loop and work for any length array.



          To create the function we must add some constraints on the array trips and what to do when we encounter any problems.



          1. That the array trips contains objects that each have the property from and to that are correctly formatted static strings. The resulting array is erroneous or indeterminate if not so.

          2. That the array does not contain circular trips shorter than the array length.

          3. That a complete trip length is no longer than the array, or when a matching trip.to can not be found. The returned array can be 0 to trips.length in size.

          4. Locations are case sensitive.

          5. If there is more than one matching trip.from it is assumed that the first match in trips is the correct one. (It would be interesting to extract the longest possible trip from? or the shortest trip that returns to the origin?)

          Example



          function tripFrom(trips, from) 
          const result = [];
          while (result.length < trips.length)
          const trip = trips.find(trip => trip.from === from);
          if (!trip) break
          from = trip.to;
          result.push(trip);

          return result;

          tripFrom(trips, "JFK");


          Or if it is known that the trip is the same length as the input array.



          function tripFrom(trips, from) 
          const res = [];
          while (res.length < trips.length)
          from = (res[res.length] = trips.find(trip => trip.from === from)).to;

          return res;

          tripFrom(trips, "JFK");


          It is unclear if you want the array sorted in place. If that is a requirement then the above version can be modified to do that by simply copying the results array res to the trips array. You can empty an array by setting its length to zero. The spread ... operator in this case spreads the array items over the functions arguments trips.push(...res) thus pushing all the items to the array.



          function tripFrom(trips, from) 
          const res = [];
          while (res.length < trips.length)
          from = (res[res.length] = trips.find(trip => trip.from === from)).to;

          trips.length = 0;
          trips.push(...res);
          return trips;

          tripFrom(trips, "JFK");






          share|improve this answer












          share|improve this answer



          share|improve this answer










          answered 1 hour ago









          Blindman67Blindman67

          9,3901622




          9,3901622





















              1












              $begingroup$

              It would be good if your function could work for more than 3 trips.



              And for larger chains of trips it becomes important to make it efficient. It is not efficient to search for the next trip by scanning the whole array. This will make the solution have O(n²) time complexity. So I would suggest creating a Map first, so that you can access a trip by its from property in constant time:






              function sortByLinked(trips, origin = "JFK") 
              const map = new Map(trips.map(trip => [trip.from, trip]));
              const result = [];
              for (let trip; trip = map.get(origin); origin = trip.to)
              result.push(trip);
              map.delete(origin);

              return result;


              const trips = [from: "DEN",to: "JFK",from: "SEA",to: "DEN",from: 'JFK', to: 'SEA'];
              const sorted = sortByLinked(trips, "JFK");
              console.log(sorted);








              share|improve this answer









              $endgroup$

















                1












                $begingroup$

                It would be good if your function could work for more than 3 trips.



                And for larger chains of trips it becomes important to make it efficient. It is not efficient to search for the next trip by scanning the whole array. This will make the solution have O(n²) time complexity. So I would suggest creating a Map first, so that you can access a trip by its from property in constant time:






                function sortByLinked(trips, origin = "JFK") 
                const map = new Map(trips.map(trip => [trip.from, trip]));
                const result = [];
                for (let trip; trip = map.get(origin); origin = trip.to)
                result.push(trip);
                map.delete(origin);

                return result;


                const trips = [from: "DEN",to: "JFK",from: "SEA",to: "DEN",from: 'JFK', to: 'SEA'];
                const sorted = sortByLinked(trips, "JFK");
                console.log(sorted);








                share|improve this answer









                $endgroup$















                  1












                  1








                  1





                  $begingroup$

                  It would be good if your function could work for more than 3 trips.



                  And for larger chains of trips it becomes important to make it efficient. It is not efficient to search for the next trip by scanning the whole array. This will make the solution have O(n²) time complexity. So I would suggest creating a Map first, so that you can access a trip by its from property in constant time:






                  function sortByLinked(trips, origin = "JFK") 
                  const map = new Map(trips.map(trip => [trip.from, trip]));
                  const result = [];
                  for (let trip; trip = map.get(origin); origin = trip.to)
                  result.push(trip);
                  map.delete(origin);

                  return result;


                  const trips = [from: "DEN",to: "JFK",from: "SEA",to: "DEN",from: 'JFK', to: 'SEA'];
                  const sorted = sortByLinked(trips, "JFK");
                  console.log(sorted);








                  share|improve this answer









                  $endgroup$



                  It would be good if your function could work for more than 3 trips.



                  And for larger chains of trips it becomes important to make it efficient. It is not efficient to search for the next trip by scanning the whole array. This will make the solution have O(n²) time complexity. So I would suggest creating a Map first, so that you can access a trip by its from property in constant time:






                  function sortByLinked(trips, origin = "JFK") 
                  const map = new Map(trips.map(trip => [trip.from, trip]));
                  const result = [];
                  for (let trip; trip = map.get(origin); origin = trip.to)
                  result.push(trip);
                  map.delete(origin);

                  return result;


                  const trips = [from: "DEN",to: "JFK",from: "SEA",to: "DEN",from: 'JFK', to: 'SEA'];
                  const sorted = sortByLinked(trips, "JFK");
                  console.log(sorted);








                  function sortByLinked(trips, origin = "JFK") 
                  const map = new Map(trips.map(trip => [trip.from, trip]));
                  const result = [];
                  for (let trip; trip = map.get(origin); origin = trip.to)
                  result.push(trip);
                  map.delete(origin);

                  return result;


                  const trips = [from: "DEN",to: "JFK",from: "SEA",to: "DEN",from: 'JFK', to: 'SEA'];
                  const sorted = sortByLinked(trips, "JFK");
                  console.log(sorted);





                  function sortByLinked(trips, origin = "JFK") 
                  const map = new Map(trips.map(trip => [trip.from, trip]));
                  const result = [];
                  for (let trip; trip = map.get(origin); origin = trip.to)
                  result.push(trip);
                  map.delete(origin);

                  return result;


                  const trips = [from: "DEN",to: "JFK",from: "SEA",to: "DEN",from: 'JFK', to: 'SEA'];
                  const sorted = sortByLinked(trips, "JFK");
                  console.log(sorted);






                  share|improve this answer












                  share|improve this answer



                  share|improve this answer










                  answered 5 hours ago









                  trincottrincot

                  44737




                  44737



























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