Press n or j to go to the next uncovered block, b, p or k for the previous block.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 | /* eslint-disable no-param-reassign */
/**
* Sorting Algorithm MergeSort
*
* Implementation based on pseudocode from Wikipedia.
*
* @author Bernhard Frick
* @param {number[]} elements
* @param {boolean} testing Set to true to test the algorithm
* @return {number[] || {do: {}[], undo: {}[]}[]}
*/
export default function MergeSort(elements, testing = false) {
const steps = [];
const input = Array.from(elements);
if (input.length === 0) {
return testing ? input : steps;
}
/**
* @param {number[]} leftArr
* @param {number[]} rightArr
* @return {number[]}
*/
function merge(leftArr, rightArr) {
const sortedArr = [];
while (leftArr.length && rightArr.length) {
if (leftArr[0] <= rightArr[0]) {
sortedArr.push(leftArr[0]);
leftArr = leftArr.slice(1);
} else {
sortedArr.push(rightArr[0]);
rightArr = rightArr.slice(1);
}
}
while (leftArr.length) {
sortedArr.push(leftArr.shift());
}
while (rightArr.length) {
sortedArr.push(rightArr.shift());
}
return sortedArr;
}
/**
* @param {number[]} arr
* @return {number[]}
*/
function mergesort(arr) {
if (arr.length < 2) {
return arr;
}
const midpoint = Math.trunc(arr.length / 2);
const leftArr = arr.slice(0, midpoint);
const rightArr = arr.slice(midpoint, arr.length);
return merge(mergesort(leftArr), mergesort(rightArr));
}
const output = mergesort(input);
return testing ? output : steps;
}
|