Problem

Given a string, find the first non-repeating character in it. For example, if the input string is "GeeksforGeeks", then the output should be 'f' and if the input string is "GeeksQuiz", then the output should be 'G'.
Input:
"GeeksforGeeks"
Output:
'f'

Solution

#include <iostream>
#include <string>
#include <unordered_map>

using namespace std;

char firstNonRepeatingChar(string s) {
    unordered_map<char, int> charCount;
    for (char c : s) {
        charCount[c]++;
    }
    for (char c : s) {
        if (charCount[c] == 1) {
            return c;
        }
    }
    return '\0';
}

int main() {
    string s = "GeeksforGeeks";
    cout << firstNonRepeatingChar(s) << endl;
    return 0;
}