【排序算法的JavaScript实现】

冒泡排序

1. let compare = (n1, n2) => n1 - n2;

• let bubbleSort = (arr, cmp = compare) => {
•   for (let i = 0; i < arr.length; i++) {
•     for (let j = i; j > 0; j--) {
•       if (cmp(arr[j], arr[j - 1]) < 0) {
•         [arr[j], arr[j - 1]] = [arr[j - 1], arr[j]];
•       }
•     }
•   }
•   return arr;
• };

插入排序

1. let insertionSort = (arr) => {

•     for (let i = 0; i < a.length; i++) {
•         let toCmp = arr[i];
•         for (let j = i; j > 0 && toCmp < a[j - 1]; j--)
•             arr[j] = a[j - 1];
•         arr[j] = toCmp;
•     }
•     return arr;
• }

选择排序

1. var selectionSort = function (arr) {

•   let i,m,j;
•   for (i = -1; ++i < a.length;) {
•     for (m = j = i; ++j < a.length;) {
•       if (arr[m] > arr[j]) m = j;
•     }
•     [arr[m], arr[i]] = [arr[i], arr[m]];
• }
• return arr;
• }

归并排序

1. let mergeSort = (arr) => {

•   if (arr.length < 2) return arr;
•   let middle = parseInt(arr.length / 2),
•   left = arr.slice(0, middle),
•   right = arr.slice(middle);
•   return merge(mergeSort(left), mergeSort(right));
• }
• let merge = (left, right) => {
•   let result = [];
•   while (left.length && right.length) {
•     left[0] <= right[0] ?
•     result.push(left.shift()) :
•     result.push(right.shift());
•   }
•   while (left.length) result.push(left.shift());
•   while (right.length) result.push(right.shift());
•   return result;
• }

快速排序

1. let quicksort = function(arr) {

•   if(arr.length <= 1) return arr;
•   let pivot = Math.floor((arr.length -1)/2);
•   let val = arr[pivot], less = [], more = [];
•   arr.splice(pivot, 1);
•   arr.forEach(function(e,i,a){
•     e < val ? less.push(e) : more.push(e);
•   });
•   return (quicksort(less)).concat([val],quicksort(more))
• }​​

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