dist-javascript-algorithms-and-data-structures/dist/algorithms/sorting/merge-sort/MergeSort.js

Algorithms and data-structures implemented on JavaScript

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = void 0;

var _Sort = _interopRequireDefault(require("../Sort"));

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

class MergeSort extends _Sort.default {
  sort(originalArray) {
    // Call visiting callback.
    this.callbacks.visitingCallback(null); // If array is empty or consists of one element then return this array since it is sorted.

    if (originalArray.length <= 1) {
      return originalArray;
    } // Split array on two halves.


    const middleIndex = Math.floor(originalArray.length / 2);
    const leftArray = originalArray.slice(0, middleIndex);
    const rightArray = originalArray.slice(middleIndex, originalArray.length); // Sort two halves of split array

    const leftSortedArray = this.sort(leftArray);
    const rightSortedArray = this.sort(rightArray); // Merge two sorted arrays into one.

    return this.mergeSortedArrays(leftSortedArray, rightSortedArray);
  }

  mergeSortedArrays(leftArray, rightArray) {
    let sortedArray = []; // In case if arrays are not of size 1.

    while (leftArray.length && rightArray.length) {
      let minimumElement = null; // Find minimum element of two arrays.

      if (this.comparator.lessThanOrEqual(leftArray[0], rightArray[0])) {
        minimumElement = leftArray.shift();
      } else {
        minimumElement = rightArray.shift();
      } // Call visiting callback.


      this.callbacks.visitingCallback(minimumElement); // Push the minimum element of two arrays to the sorted array.

      sortedArray.push(minimumElement);
    } // If one of two array still have elements we need to just concatenate
    // this element to the sorted array since it is already sorted.


    if (leftArray.length) {
      sortedArray = sortedArray.concat(leftArray);
    }

    if (rightArray.length) {
      sortedArray = sortedArray.concat(rightArray);
    }

    return sortedArray;
  }

}

exports.default = MergeSort;