Shared code

#include "bits/stdc++.h"
#define int long long
using namespace std;

int n;

void solve(int x,string &s, string temp,vector<int> taken,set<string> &res){
    if(x==n){
        res.insert(temp);
        return;
    }
    for(int i=0;i<n;++i){
        if(!taken[i]){
            temp.push_back(s[i]);
            taken[i]=1;
            solve(x+1,s,temp,taken,res);
            taken[i]=0; // backtrack
            temp.pop_back(); // backtrack
        }
    }
}

signed main(){
    string s;
    cin>>s;
    n=s.size();
    set<string> res;
    vector<int> taken(n,0);
    string temp;
    solve(0,s,temp,taken,res);
    cout<<res.size()<<endl;
    for(const string &x:res)cout<<x<<endl;
    return 0;
}