快排：大于等于的放右边

左边的都小于key，右边的都大于等于key
java实现：

import java.util.*;
public class Quick_Sort {
    public static void main(String[] args) {
        List<Integer> list = new ArrayList<>();
        Scanner in = new Scanner(System.in);
        while(in.hasNext()) {
            String s = in.nextLine().replace(" ", "");  //只针对0到9，范围以外需要修改输入判断
            int len = s.length();
            for (int i = 0; i < len; i++) {   //去除无用空格,只针对0到9，范围以外需要修改输入判断
                list.add(Integer.parseInt(String.valueOf(s.charAt(i))));
            }
            q_rec(list,0,list.size()-1);    //调用递归
            System.out.println(list);
        }
    }
//排序方法，保证前面数小于key对应的数，后面数大于等于key对应的数
    private static int q_sort(List<Integer> list, int from, int to) {
        int start = from;
        int end = to;
        int key = list.get(start);
        while (start < end) {
            while (end > start && list.get(end) >= key) {   //从后往前找到第一个小于key对应的数
                end--;
            }
            if (end > start) {  //找到小于key的则覆盖
                list.set(start, list.get(end));
                start++;
            } else {
                break;
            }
            while (start < end && list.get(start) < key) {  ////从前往后找到第一个大于等于key对应的数
                start++;
            }
            if (start < end) {  //找到大于等于key的则覆盖
                list.set(end, list.get(start));
                end--;
            } else {
                break;
            }
        }
        list.set(start, key);
        return start;
    }
//递归调用排序方法
    private static void q_rec(List<Integer> list ,int from,int to){ 
        if(from < to){
            int flag = q_sort(list, from, to);
            q_rec(list, from, flag-1);
            q_rec(list, flag+1, to);
        }
    }
}

js实现：

function quick_swap(arr,start,end){
    var key = arr[start];
    var left = start;
    var right = end;
    while(left < right){
        while(left < right && arr[right] > key){
            right--;
        }
        if(left < right){
            arr[left] = arr[right];
            left++;
        }
        while(left < right && arr[left] <= key){
            left++;
        }
        if(left < right) {
            arr[right] = arr[left];
            right--;
        }
    }
    arr[left] = key;
    return left;
}
function quick_rec(arr,start,end){
    if(start < end){
        var flag = quick_swap(arr,start,end);
        quick_rec(arr,start,flag-1);
        quick_rec(arr,flag+1,end);
    }
}
function quick_sort(array){
    var arr = array.concat();
    var len = arr.length;
    quick_rec(arr,0,len-1);
    alert(arr);
}

转载于:https://www.cnblogs.com/zawjdbb/p/7125248.html