排列问题
#include <iostream>
#include <cstring>
#include <cstdio>
#include <algorithm>
using namespace std;
const int N = 10;
int n;
int a[N],nums[N];
bool st[N];

void dfs(int u){
    if(u == n){
        for(int i = 0;i < n;++i)    printf("%d ",nums[i]);
        puts("");
        return;
    }
    for(int i = 0;i < n;++i){
        if(!st[i]){
            nums[u] = a[i];
            st[i] = true;
            dfs(u + 1);
            st[i] = false;
            while(i + 1 < n && a[i + 1] == a[i]) i++;
        }
    }
}

int main(){
    scanf("%d",&n);
    for(int i = 0;i < n;++i)    scanf("%d",&a[i]);
    sort(a,a + n);
    dfs(0);
    return 0;
}

#include <iostream>
#include <cstring>
#include <cstdio>
#include <algorithm>
using namespace std;
const int N = 10;
int n;
int a[N];

int main(){
    scanf("%d",&n);
    for(int i = 0;i < n;++i)    scanf("%d",&a[i]);
    sort(a,a + n);
    do{
        for(int i = 0;i < n;++i)    printf("%d ",a[i]);
        puts("");
    }while(next_permutation(a,a + n));
    return 0;
}