C++ 代码

注意死循环

当长度为2的时候，容易陷入死循环，因此递归的时候注意j j+1还是 i-1 i

注意x的取值

为了减少复杂度 x = q[(l + r) / 2]

# include <iostream>
using namespace std;
const int N = 1e5 + 10;
int q[N];
void quick_sort(int q[], int l, int r)
{
    if (l >= r) return;
    int x = q[(l + r) / 2], i = l - 1, j = r + 1;
    while(i < j)
    {
        do i ++; while (q[i] < x);
        do j --; while (q[j] > x);
        if(i < j) swap(q[i], q[j]);
    }
    quick_sort(q, l, j);
    quick_sort(q, j + 1, r);
}
int main()
{
    int n;
    scanf("%d", &n);
    for (int i = 0; i < n; i ++) scanf("%d", &q[i]);
    quick_sort(q, 0, n - 1);
    for (int i = 0; i < n; i ++) printf("%d ", q[i]);
    return 0;
}

STL

# include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 10;
int a[N], n;
int main()
{
    ios::sync_with_stdio(false);
    cin >> n;
    for(int i = 0; i < n; i ++) cin >> a[i];
    sort(a, a + n);
    for(int i = 0; i < n; i ++) cout << a[i] << " ";
    cout << endl;
    return 0;
}