Remove Duplicates using Recursion in C++

 #include<iostream>

#include<vector>

#include<cmath>

using namespace std;

void removeDuplicates(string str, string ans, int i, int map[26]) {

    // Base case

    if(i == str.size()) {

        cout << "ans: " << ans << endl;

    return;

    }

    int mapIdx = (int)(str[i] - 'a');

    if(map[mapIdx]) { // duplicate

            removeDuplicates(str, ans, i+1, map);

    } else {// not duplicate

    map[mapIdx] = true;

    removeDuplicates(str, ans+str[i], i+1, map);

    }

}

int main() {

    string str = "appnnacollege";

    string ans = "";

    int map[26] = {false};

    removeDuplicates(str, ans,0, map);

return 0;

}