几种排序算法的JavaScript实现-蒲公英云

几种排序算法的JavaScript实现

/** * Created by lzc on 2017/4/30. */
var a = (function (){ 
    var a = [];
    function randomInt(from, to){ 
        return parseInt(Math.random() * (to - from + 1) + from);
    }
    for (var i = 0; i < 10000; i++){
        a.push(randomInt(0, 1000000))
    }
    return a;
})();
/** * 插入排序 */
function insertionSort(){ 
    var date = new Date();
    for (var i = 1; i < a.length; i++){
        var temp = a[i];
        for (var j = i - 1; j >= 0 && a[j] > temp; j--){
            a[j + 1] = a[j];
        }
        a[j + 1] = temp;
    }
    console.log("插入排序的时间：" + (new Date() - date));
}
/** * 希尔排序 */
function shellSort(){ 
    var date = Date.now();
    for (var gap = a.length >> 1; gap > 0; gap >>= 1){
        for (var i = gap; i < a.length; i++){
            var temp = a[i];
            for (var j = i - gap; j >= 0 && a[j] > temp; j -= gap){
                a[j + gap] = a[j];
            }
            a[j + gap] = temp;
        }
    }
    console.log("希尔排序的时间：" + (new Date() - date));
}
/** * 归并 * @param a * @param b * @param lo * @param mid * @param hi */
function merge(a, b, lo, mid, hi){ 
    //每次归并前，都需要先把a中的数据copy到b中。
    for (var i = 0; i < a.length; i++){
        b[i] = a[i];
    }
    var i = lo, j = mid + 1;
    for (var k = lo; k <= hi; k++){
        if (i > mid){
            a[k] = b[j++];
        }else if (j > hi){
            a[k] = b[i++];
        }else if (b[i] < b[j]){
            a[k] = b[i++];
        }else{
            a[k] = b[j++]
        }
    }
}
/** * 归并排序 * @param a * @param temp * @param lo * @param hi */
function sort(a, temp, lo, hi){ 
    if (lo >= hi) return;
    var mid = (hi + lo) >> 1;
    sort(a, temp, lo, mid);  //左半部分排序
    sort(a, temp, mid + 1, hi);//右半部分排序
    merge(a, temp, lo, mid, hi);
}
/** * 快速排序 */
function quickSort(a, lo, hi){ 
    if (lo >= hi) return;
    var j = quickPartition(a, lo, hi);
    quickSort(a, lo, j - 1);
    quickSort(a, j + 1, hi);
}
/** * 快速排序的切分 * @param a * @param lo * @param hi */
function quickPartition(a, lo, hi){ 
    var i = lo, j = hi + 1;  //左右扫描指针
    var p = a[lo];  //切分元素
    for (; ;){
        //扫描左右,检查扫描是否结束，并交换元素
        while (a[++i] <= p){
            if (i == hi) break;
        }
        while (a[--j] >= p){
            if (j == lo) break;
        }
        //如果左指针超过了右指针则结束
        if (i >= j) break;
        //交换左右的元素
        exch(a, i, j);
    }
    //把a[lo]添加到指定的位置
    exch(a, lo, j);
    return j;
}
function exch(a, m, n){ 
    var temp = a[m];
    a[m] = a[n];
    a[n] = temp;
}
//--测试开始
var date = new Date()
quickSort(a, 0, a.length - 1);
console.log("快速排序时间：" + (new Date() - date));
console.log(a.toString());