js 排序算法总结

1.冒泡排序 

平均时间复杂度O(N²) 最好情况O(N)最坏情况O(N²) 空间复杂度O(1)

function bubbleSort(arr){if(arr.length <= 1)return arr;var flag = 1;             // 标识是否进行交换for(var i=0; i < arr.length; i++){if(i !=0 && flag) break;for(var j=0; j < arr.length-i-1; j++){if(arr[j] > arr[j+1]){if(flag == 1) flag = 0;var temp = arr[j];arr[j] = arr[j+1];arr[j+1] = temp;}}    }return arr;
}
var a = [2, 3, 4, 5, 15, 19, 26, 27, 36, 38, 44, 46, 47, 48, 50];
console.log(bubbleSort(a));

升级版冒泡排序

function bubbleSort2(arr) {var low = 0;var high= arr.length-1; //设置变量的初始值var tmp,j;console.time('2.改进后冒泡排序耗时');while (low < high) {for (j= low; j< high; ++j) {         //正向冒泡,找到最大者if (arr[j]> arr[j+1]) {tmp = arr[j]; arr[j]=arr[j+1];arr[j+1]=tmp;}}--high;  //修改high值, 前移一位for (j=high; j>low; --j) {          //反向冒泡,找到最小者if (arr[j]<arr[j-1]) {tmp = arr[j]; arr[j]=arr[j-1];arr[j-1]=tmp;}}　++low;  //修改low值,后移一位
　　}console.timeEnd('2.改进后冒泡排序耗时');return arr;
}
var arr=[3,44,38,5,47,15,36,26,27,2,46,4,19,50,48];
console.log(bubbleSort2(arr));

 

2.选择排序

平均时间复杂度O(N²) 最好情况O(N²)最坏情况O(N²) 空间复杂度O(1)  适合小数据（1000以内）排序

function selectionSort(arr) {var len = arr.length;var minIndex, temp;console.time('选择排序耗时');for (var i = 0; i < len - 1; i++) {minIndex = i;for (var j = i + 1; j < len; j++) {if (arr[j] < arr[minIndex]) { //寻找最小的数minIndex = j; //将最小数的索引保存
　　　　　　}}temp = arr[i];arr[i] = arr[minIndex];arr[minIndex] = temp;}console.timeEnd('选择排序耗时');return arr;
}
var arr=[3,44,38,5,47,15,36,26,27,2,46,4,19,50,48];
console.log(selectionSort(arr));

3. 插入排序

平均时间复杂度O(N²) 最好情况O(N)最坏情况O(N²) 空间复杂度O(1)

function insertionSort(array) {console.time('插入排序耗时：');for (var i = 1; i < array.length; i++) {var key = array[i];var j = i - 1;while ( array[j] > key) {array[j + 1] = array[j];j--;}array[j + 1] = key;}console.timeEnd('插入排序耗时：');return array;
}
var arr=[3,44,38,5,47,15,36,26,27,2,46,4,19,50,48];
console.log(insertionSort(arr));

升级版（通过二分法查找左边有序数组中待差数字的插入位置）

function binaryInsertionSort(array) {console.time('二分插入排序耗时：');for (var i = 1; i < array.length; i++) {var key = array[i], left = 0, right = i - 1;while (left <= right) {var middle = parseInt((left + right) / 2);if (key < array[middle]) {right = middle - 1;} else {left = middle + 1;}}for (var j = i - 1; j >= left; j--) {array[j + 1] = array[j];}array[left] = key;}console.timeEnd('二分插入排序耗时：');return array;
}
var arr=[3,44,38,5,47,15,36,26,27,2,46,4,19,50,48];
console.log(binaryInsertionSort(arr));

4. 快速排序

平均时间复杂度O(NlogN) 最好情况O(NlogN)最坏情况O(N²) 空间复杂度O(logN)

function quickSort(arr){if(arr.length <= 1) return arr;var pivotIndex = Math.floor(arr.length/2);var pivot = arr.splice(pivotIndex,1)[0];var left = [];var right = [];for(var i = 0; i < arr.length; i++){if(arr[i] < pivot){left.push(arr[i]);}else{right.push(arr[i]);}}return quickSort(left).concat([pivot],quickSort(right));
}
var arr=[2,3,1];
console.log(quickSort(arr));