kuaisupaixu

快速排序，要求用 fun(int*a,int n),n是数组长度,不知道哪儿错了

void fun(int* a, int n)
{
    int i = 0, j = n;
    int x = a[i];

    while (i < j)
    {
        while (i < j && a[j] >= x) { j--; }
        if (i < j) { a[i] = a[j]; }
        while (i < j && a[i] <= x) { i++; }
        if (i < j) { a[j] = a[i]; }
    }
    a[i] = x;
    fun(a-i-1, i);
    fun(a-i+1, n-i);
}

int main()
{
    int a[100];
    int n;
    cout << "请输入要排序的个数：";
    cin >> n;
    cout << "请输入" << n << "个数：";
    for (int i = 0; i < n; i++)
    {
        cin >> a[i];
    }
    fun(a, n);
    cout << "排序为：";
    for (int j = 0; j < n; j++)
    {

        cout << a[j] << " ";
    }
    cout << endl;
    return 0;
}

选择排序参考代码如下：

void fun(int* a, int n) {
    
    if (n < 2) {
        
        return;
    }
    for (int i = 0; i < n - 1; i++) {
        
        for (int j = i + 1; j < n; j++) {
            
            if (a[i] > a[j]) {
                
                int temp = a[i];
                a[i] = a[j];
                a[j] = temp;
            }
        }
    }
}

if (i < j) { a[i] = a[j]; }
这是干啥呢？这么赋值不就覆盖掉了？至少得交换吧

这个不是快排吧，给你个参考：

#include<iostream>
using namespace std;
//交换函数swap
void swap1(int& a, int& b)
{
    int temp = a; a = b; b = temp;
}
//做一个把数组分两半的函数
int sortSecond(int A[], int low, int high)
{
    int P = A[high];//基数选择右边界
    while (low < high)
    {
        while (low < high && A[low] <= P)
            low++;//左边部分小的跳过
        if (low < high){
            swap1(A[low], A[high--]);//大的扔到后面并使右边界减一
        }
        while (low<high && A[high]>=P)
            high--;//右边大的跳过
        if (low < high) {
            swap1(A[low++], A[high]);//小的扔到前面并使左边界加一
        }
    }
    return low;//此时low=high
}
void fastSort(int A[], int low, int high)
{
    if (low > high) return;//递归结束条件 low>high
    int v = sortSecond(A, low, high);
    fastSort(A, low,  v - 1);//对左区间递归排序
    fastSort(A, v + 1, high);//对右区间递归排序
}
int main()
{
    int A[9] = {4,3,1,2,4,9,5,8,6};
    int len = sizeof(A) / sizeof(A[0]);
    cout << "排序前数组为：\t" << endl;
    for (int i = 0; i < len; i++)
    {
        cout << A[i] << " ";
    }
    cout << endl;
    fastSort(A, 0, len-1);//时间复杂度 平均情况O(nlogn)，最坏情况O(n^2)
    cout << "快速排序后数组为：\t" << endl;
    for (int i = 0; i < len; i++)
    {
        cout << A[i] << " ";
    }
}

我以为写完就完事了，没想到老师又说这不是快排，我滴个天，还要咋样才叫快排