Online C++ Compiler

#include<bits/stdc++.h>
#include<iostream>
using namespace std;
set<string> sem;

void solve(string s, int i) {
    if (i == s.size()) {
        sem.insert(s);
        return;
    }
    for (int k = i; k < s.size(); k++) {
        swap(s[i], s[k]);
        solve(s, i + 1);
        swap(s[i], s[k]);
    }
}

int main() {
    string s = "hello";
    solve(s, 0);
    cout << sem.size() << endl;
    for (auto it = sem.begin(); it != sem.end(); it++) {
        cout << *it << endl;
    }
    return 0;
}