How To Rearrange An Array By Indices Array (proof)?

Given an array arr and an array of indices ind, the following algorithm rearranges arr in-place to satisfy the given indices: function swap(arr, i, k) { var temp = arr[i]; arr[

Solution 1:

This algorithm does not work, it's enough to show a counter-example:

var arr = ["A", "B", "C", "D"];
var ind = [  2,   3,   1,   0];

rearrange(arr, ind);
console.log(arr); // => ["C", "D", "A", "B"]

A working alternative may be

function swap(arr, i, k) {
  var temp = arr[i];
  arr[i] = arr[k];
  arr[k] = temp;
}

function rearrange(arr, ind) {
  for (var i = 0, len = arr.length; i < len; i++) {
    if (ind[i] !== i) {
      swap(arr, i, ind[i]);
      swap(ind, i, ind[i]);
      if (ind[i] < i) {
        i = ind[i]-1;
      }
    }
  }
}