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Add several more comments to in place quick sort.

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This commit is contained in:
Oleksii Trekhleb 2018-09-14 17:21:51 +03:00
parent 66f19d65c5
commit 46bc844fc6
1 changed files with 12 additions and 10 deletions
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22
src/algorithms/sorting/quick-sort/QuickSortInPlace.js
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@ -6,10 +6,11 @@ export default class QuickSortInPlace extends Sort {
* This process is difficult to describe, but much clearer with a visualization: * This process is difficult to describe, but much clearer with a visualization:
* @see: http://www.algomation.com/algorithm/quick-sort-visualization * @see: http://www.algomation.com/algorithm/quick-sort-visualization
* *
* @param {*[]} originalArray * @param {*[]} originalArray - Not sorted array.
* @param {number} inputLowIndex * @param {number} inputLowIndex
* @param {number} inputHighIndex * @param {number} inputHighIndex
* @return {*[]} * @param {boolean} recursiveCall
* @return {*[]} - Sorted array.
*/ */
sort( sort(
originalArray, originalArray,
@ -21,18 +22,19 @@ export default class QuickSortInPlace extends Sort {
const array = recursiveCall ? originalArray : [...originalArray]; const array = recursiveCall ? originalArray : [...originalArray];
/** /**
* `partition` operates on the subarray between lowIndex and highIndex, inclusive. * The partitionArray() operates on the subarray between lowIndex and highIndex, inclusive.
* it arbitrarily chooses the last element in the subarray as the pivot. * It arbitrarily chooses the last element in the subarray as the pivot.
* then, it partially sorts the subarray into elements than are less than the pivot, * Then, it partially sorts the subarray into elements than are less than the pivot,
* and elements that are greater than or equal to the pivot. * and elements that are greater than or equal to the pivot.
* each time `partition` is executed, the pivot element is in its final sorted position. * Each time partitionArray() is executed, the pivot element is in its final sorted position.
* *
* @param {number} lowIndex * @param {number} lowIndex
* @param {number} highIndex * @param {number} highIndex
* @return {number} * @return {number}
*/ */
const partition = (lowIndex, highIndex) => { const partitionArray = (lowIndex, highIndex) => {
/** /**
* Swaps two elements in array.
* @param {number} leftIndex * @param {number} leftIndex
* @param {number} rightIndex * @param {number} rightIndex
*/ */
@ -43,7 +45,7 @@ export default class QuickSortInPlace extends Sort {
}; };
const pivot = array[highIndex]; const pivot = array[highIndex];
// visitingCallback is used for time-complexity analysis // visitingCallback is used for time-complexity analysis.
this.callbacks.visitingCallback(array[pivot]); this.callbacks.visitingCallback(array[pivot]);
let partitionIndex = lowIndex; let partitionIndex = lowIndex;
@ -63,9 +65,9 @@ export default class QuickSortInPlace extends Sort {
return partitionIndex; return partitionIndex;
}; };
// Base case is when low and high converge // Base case is when low and high converge.
if (inputLowIndex < inputHighIndex) { if (inputLowIndex < inputHighIndex) {
const partitionIndex = partition(inputLowIndex, inputHighIndex); const partitionIndex = partitionArray(inputLowIndex, inputHighIndex);
const RECURSIVE_CALL = true; const RECURSIVE_CALL = true;
this.sort(array, inputLowIndex, partitionIndex - 1, RECURSIVE_CALL); this.sort(array, inputLowIndex, partitionIndex - 1, RECURSIVE_CALL);
this.sort(array, partitionIndex + 1, inputHighIndex, RECURSIVE_CALL); this.sort(array, partitionIndex + 1, inputHighIndex, RECURSIVE_CALL);