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;
}