关于JS的算法

一.快速排序

function qSort(arr) {
    if(arr.length === 0) {
        return [];
    }

    var left = [];
    var right = [];
    var pivot = arr[0];

    for (var i = 1; i < arr.length; i++) {//从i=1开始
        if(arr[i] < pivot) {
            left.push(arr[i]);
        }else {
            right.push(arr[i]);
        }
    }
    return qSort(left).concat(pivot, qSort(right));
}//快速排序

window.onload = function() {
    var a = [];
    for (var i = 0; i < 10; ++i) {
       a[i] = Math.floor((Math.random()*100)+1);
    }
    console.log(a);
    console.log(qSort(a));//快速排序
}

　　

二.插入排序

function insertionSort(arr) {
    var temp, inner;
    console.log(arr);
    for(var outer = 1; outer < arr.length; outer++) {
        temp = arr[outer];
        inner = outer;
        while(inner > 0 && (arr[inner - 1] >= temp)) {
            arr[inner] = arr[inner - 1];
            inner--;
        }
        arr[inner] = temp;
    }
    return arr;
}//插入排序

window.onload = function() {
    var a = [];
    for (var i = 0; i < 10; ++i) {
       a[i] = Math.floor((Math.random()*100)+1);
    }
    console.log(a);
    console.log(insertionSort(a));//插入排序
}

　　

三.选择排序法

    function selectionSortMax(arr) {
        var max;
        for(var outer = 0; outer < arr.length; outer++) {
            max = 0;
            for(var inner = 0; inner < arr.length - outer; inner++) {
                if(arr[inner] > arr[max]) {
                    max = inner;
                }
            }
            swap(arr, max, arr.length - outer - 1);
        }
        return arr;
    }//选择排序法选择最大值移到最后

    function selectionSortMin(arr) {
        var min, temp;
        for(var outer = 0; outer < arr.length - 1; outer++) {
            min = outer;
            for(var inner = outer + 1; inner < arr.length; inner++) {
                if(arr[inner] < arr[min]) {
                    min = inner;
                }
            }
            swap(arr, min, outer);
        }
        return arr;
    }//选择排序法选择最小值移到最前

    function swap(arr, index1, index2) {
        var temp = arr[index2];
        arr[index2] = arr[index1];
        arr[index1] = temp;
    }

    window.onload = function() {
        var a = [];
        for (var i = 0; i < 10; ++i) {
           a[i] = Math.floor((Math.random()*100)+1);
        }
        console.log(a);
        console.log(selectionSortMax(a));
        console.log(selectionSortMin(a));
    }

　　

四.冒泡排序法

function bubbleSort(arr) {
    var temp;
    for(var outer = arr.length; outer > 1; outer--) {
        for(inner = 0; inner < outer - 1; inner++) {
            if(arr[inner] > arr[inner + 1]) {
                swap(arr, inner, inner + 1);
            }
        }
    }
    return arr;
}//冒泡排序法

function swap(arr, index1, index2) {
    var temp = arr[index2];
    arr[index2] = arr[index1];
    arr[index1] = temp;
}

window.onload = function() {
    var a = [];
    for (var i = 0; i < 10; ++i) {
       a[i] = Math.floor((Math.random()*100)+1);
    }
    console.log(a);
    console.log(bubbleSort(a));//冒泡排序法
}

五.归并算法

function mergeSortRec(array) {
        var length = array.length;
        if(length == 1) {
            return array;
        }

        var mid = Math.floor(length / 2);
        var left = array.slice(0, mid);
        var right = array.slice(mid, length);

        return merge(mergeSortRec(left), mergeSortRec(right));
    }

function merge(left, right) {
    var result = [];
    var il = 0;
    var ir = 0;
    while(il < left.length && ir < right.length) {
        if(left[il] < right[ir]) {
            result.push(left[il++]);
        }else {
            result.push(right[ir++]);
        }
    }

    while(il < left.length) {
        result.push(left[il++]);
    }

    while(ir < right.length) {
        result.push(right[ir++]);
    }

    return result;
}

window.onload = function() {
    var a = [];
    for (var i = 0; i < 10; ++i) {
       a[i] = Math.floor((Math.random()*100)+1);
    }
    console.log(a);
    console.log(mergeSortRec(a));//归并排序法
}

通过时间戳可以得到快速排序>选择排序>插入排序>冒泡排序。