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Created September 9, 2013 06:49
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QuickSort In Place (in JavaScript)
// quicksort using new arrays is easy, but surprisingly, there weren't too many examples
// in javascript of in-place quick sort...
// the outer function is simply just a wrapper that copies the original array;
// you can just use lines 12-37 if preserving the original array isn't important
function quickSortInPlace(unsortedArray) {
var unsorted = unsortedArray.slice(); // copy the original array
// lb, rb - left bound, right bound
function qSort(unsorted, lb, rb) {
if(typeof lb === 'undefined') { lb = 0; }
if(typeof rb === 'undefined') { rb = unsorted.length-1; }
if(lb < rb) {
var pivot = unsorted[Math.floor((lb+rb)/2)];
var l = lb, r = rb; // index variables that travel from either end
var tmpSwap;
// what some people call the partitioning
while(l < r) {
while(unsorted[l] < pivot) { l++; }
while(pivot < unsorted[r]) { r--; }
if(l <= r) {
tmpSwap = unsorted[l];
unsorted[l] = unsorted[r];
unsorted[r] = tmpSwap;
qSort(unsorted, lb, r);
qSort(unsorted, l, rb);
return unsorted;
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ftripier commented Sep 9, 2013

Please instantiate qSort in global scope, and then simply call it using parameters from quickSortInPlace's local scope.

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