Create mergeSort.js (yangshun#38)

Author: jorgegonzalez

utilities/javascript/mergeSort.js

@@ -0,0 +1,54 @@
+function mergeSort(arr) {
+ if (arr.length < 2) {
+ // Arrays of length 0 or 1 are sorted by definition
+ return arr;
+ }
+
+ const left = arr.slice(0, Math.floor(arr.length / 2));
+ const right = arr.slice(Math.floor(arr.length / 2), Math.floor(arr.length));
+
+ return merge(mergeSort(left), mergeSort(right));
+}
+
+function merge(arr1, arr2) {
+ const merged = [];
+
+ let i = 0;
+ let j = 0;
+
+ while (i < arr1.length && j < arr2.length) {
+ if (arr1[i] < arr2[j]) {
+ merged.push(arr1[i]);
+ i++;
+ } else if (arr2[j] < arr1[i]) {
+ merged.push(arr2[j]);
+ j++;
+ } else {
+ merged.push(arr1[i]);
+ i++;
+ j++;
+ }
+ }
+
+ while (i < arr1.length) {
+ merged.push(arr1[i]);
+ i++;
+ }
+
+ while (j < arr2.length) {
+ merged.push(arr2[j]);
+ j++;
+ }
+
+ return merged;
+}
+
+const arr1 = [7, 2, 4, 3, 1, 2];
+const arr2 = [10, 9, 8, 7, 6, 5, 4, 3, 2, 1];
+const arr3 = [98322, 3242, 876, -234, 34, 12331];
+const arr4 = [1, 2, 3, 4, 5, 0];
+
+console.log(mergeSort(arr1));
+console.log(mergeSort(arr2));
+console.log(mergeSort(arr3));
+console.log(mergeSort(arr4));