STL库

#include<bits/stdc++.h>
using namespace std;
const int N=1e5+5,INF=0x3f3f3f3f;
typedef long long LL;
int a,b[9];
int ans;
int main()
{
	cin>>a;
	for(int i=1;i<=a;i++)b[i] = i;
	do{
		for(int i=1;i<=a;i++)cout<<b[i];
		cout<<endl;
		ans++;
	}while(next_permutation(b+1,b+a+1));
	cout<<ans;
	return 0;
}

#include <iostream>
using namespace std;
int a[100],n,cnt;
bool b[100];
 
void dfs(int dep){
    if(dep > n){
        for(int i = 1;i <= n;i++){
            printf("%d", a[i]);
        }
        cnt++;
        putchar('\n');
        putchar('\n');
        return;
    }
    for(int i = 1;i <= n;i++){
        if(b[i] == false){
            a[dep] = i;
            b[i] = true;
            dfs(dep+1);
            b[i] = false;
        }
    }
}
 
int main(){
    scanf("%d", &n);
    dfs(1);
    printf("%d\n", cnt);
    return 0;
}