#include<bits/stdc++.h>
using namespace std;
long i,j,n,s;
string b;
char a[505];
int main()
{
	cin>>n>>b;
	for(i=1;i<=n;i++)a[i]=b[i-1];
    sort(a+1,a+n+1);
	do{
		for(i=1;i<=n;i++)cout<<a[i];
		cout<<endl;s++;
	}while(next_permutation(a+1,a+n+1));stl
	cout<<s;
	return 0;
}

大法师求解即可。

#include <bits/stdc++.h>
using namespace std;
const int N = 155;
int n, sum, cnt[N];
vector<int> ans;
char ch;
void dfs(int depth) {
	if (depth == n) {
		for (char i : ans)
			cout << i;
		cout << '\n', sum ++;
		return;
	}
	for (int i = 'a'; i <= 'z'; i ++)
		if (cnt[i]) cnt[i] --, ans.push_back(i), dfs(depth + 1), ans.pop_back(), cnt[i] ++;
}
int main() {
	cin >> n;
	for (int i = 1; i <= n; i ++)
		cin >> ch, cnt[ch] ++;
	dfs(0);
	cout << sum << '\n';
	return 0;
}