sort array keys by value

Question

I'm using javascript, and I have an array containing multiple values, which may be non-unique. I'd like to take this array and generate a new array, or ordered list, of its keys in ascending order of value. For example, if I have [ 2, 2, 4, 5, 1, 6 ], I'd like to generate [ 5, 4, 0, 1, 2, 3 ].

I was thinking of iterating over the original list and inserting each value into the new list while checking for proper placement by comparing to the existing values of the new list every time an insertion is performed. This seems wasteful, though, as I'd have to (potentially) check every value of the new list for every insertion.

Anyone have a simpler method for this?

How does [5,4,0,1,2,3] follow from [2,2,4,5,1,6]?

Alex
– Alex

2016-12-13 02:51:36 +00:00
Commented Dec 13, 2016 at 2:51 — Alex
– Alex, Commented Dec 13, 2016 at 2:51

Lightness Races in Orbit · Accepted Answer · 2012-02-03 01:40:52Z

4

I think you meant [ 4, 0, 1, 2, 3, 5 ].

function GetSortedKeys(values) {

   var array_with_keys = [];
   for (var i = 0; i < values.length; i++) {
       array_with_keys.push({ key: i, value: values[i] });
   }

   array_with_keys.sort(function(a, b) {
      if (a.value < b.value) { return -1; }
      if (a.value > b.value) { return  1; }
      return 0;
   });

   var keys = [];
   for (var i = 0; i < array_with_keys.length; i++) {
       keys.push(array_with_keys[i].key);
   }

   return keys;
}

var array = [2, 2, 4, 5, 1, 6];
alert(GetSortedKeys(array));

This is the simplest method I can come up with on Javascript, unfortunately.

edited Feb 3, 2012 at 1:40

answered Mar 16, 2011 at 15:12

Lightness Races in Orbit

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5 Comments

Pete Over a year ago

This works and I like it better than what I had worked out. Thanks

Lightness Races in Orbit Over a year ago

I've since learned how we should iterate over arrays. See my edit.

Lightness Races in Orbit Over a year ago

@Athari: Could that be because this is not a sorting algorithm, do you think?

LordAro Over a year ago

ah, but the question has the 'sorting' tag, so you can forgive the mistake :)

Lightness Races in Orbit Over a year ago

@LordAro This is why one shall not make assumptions based upon a mere tag. :)

Iulius Curt · Accepted Answer · 2013-04-25 17:31:26Z

0

Using the nice Underscore.JS:

var get_sorted_keys = function(values) {
    var keys_idx = [], i;
    for (i = 0; i < values.length; i++) {
        keys_idx.push(i);
    }

    var keys = _.sortBy(keys_idx, function(idx){ return values[idx]; });

    return keys;
};

var array = [2, 2, 4, 5, 1, 6];
console.log("Sorted keys:", get_sorted_keys(array));

Output:

Sorted keys: [4, 0, 1, 2, 3, 5]

answered Apr 25, 2013 at 17:31

Iulius Curt

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