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optimized version of mergesort code

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bryanspacex 2023-07-11 23:29:38 +05:30
parent 8c5e5f4f0d
commit 8a930141a0
1 changed files with 22 additions and 25 deletions
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47
src/algorithms/sorting/merge-sort/MergeSort.js
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@ -5,7 +5,7 @@ export default class MergeSort extends Sort {
// Call visiting callback. // Call visiting callback.
this.callbacks.visitingCallback(null); this.callbacks.visitingCallback(null);
// If array is empty or consists of one element then return this array since it is sorted. // If array is empty or consists of one element then return this array since it is already sorted.
if (originalArray.length <= 1) { if (originalArray.length <= 1) {
return originalArray; return originalArray;
} }
@ -13,48 +13,45 @@ export default class MergeSort extends Sort {
// Split array on two halves. // Split array on two halves.
const middleIndex = Math.floor(originalArray.length / 2); const middleIndex = Math.floor(originalArray.length / 2);
const leftArray = originalArray.slice(0, middleIndex); const leftArray = originalArray.slice(0, middleIndex);
const rightArray = originalArray.slice(middleIndex, originalArray.length); const rightArray = originalArray.slice(middleIndex);
// Sort two halves of split array // Sort two halves of split array.
const leftSortedArray = this.sort(leftArray); const sortedLeftArray = this.sort(leftArray);
const rightSortedArray = this.sort(rightArray); const sortedRightArray = this.sort(rightArray);
// Merge two sorted arrays into one. // Merge two sorted arrays into one.
return this.mergeSortedArrays(leftSortedArray, rightSortedArray); return this.mergeArrays(sortedLeftArray, sortedRightArray);
} }
mergeSortedArrays(leftArray, rightArray) { mergeArrays(leftArray, rightArray) {
const sortedArray = []; let sortedArray = [];
// Use array pointers to exclude old elements after they have been added to the sorted array. // Indices for traversing the left and right arrays.
let leftIndex = 0; let leftIndex = 0;
let rightIndex = 0; let rightIndex = 0;
while (leftIndex < leftArray.length && rightIndex < rightArray.length) { while (leftIndex < leftArray.length && rightIndex < rightArray.length) {
let minElement = null; // Compare the elements at the current indices.
const leftElement = leftArray[leftIndex];
const rightElement = rightArray[rightIndex];
// Find the minimum element between the left and right array. if (this.comparator.lessThanOrEqual(leftElement, rightElement)) {
if (this.comparator.lessThanOrEqual(leftArray[leftIndex], rightArray[rightIndex])) { // If the left element is smaller or equal, append it to the sorted array.
minElement = leftArray[leftIndex]; sortedArray.push(leftElement);
// Increment index pointer to the right
leftIndex += 1; leftIndex += 1;
} else { } else {
minElement = rightArray[rightIndex]; // Otherwise, append the right element to the sorted array.
// Increment index pointer to the right sortedArray.push(rightElement);
rightIndex += 1; rightIndex += 1;
} }
// Add the minimum element to the sorted array.
sortedArray.push(minElement);
// Call visiting callback. // Call visiting callback.
this.callbacks.visitingCallback(minElement); this.callbacks.visitingCallback(null);
} }
// There will be elements remaining from either the left OR the right // Concatenate the remaining elements from either the left or the right array.
// Concatenate the remaining elements into the sorted array sortedArray = sortedArray.concat(leftArray.slice(leftIndex)).concat(rightArray.slice(rightIndex));
return sortedArray
.concat(leftArray.slice(leftIndex)) return sortedArray;
.concat(rightArray.slice(rightIndex));
} }
} }