Find the First Non-Repeating Character in a String

Problem

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

Solution

This solution is in C++. Our A.I. can create solutions in multiple languages.

kayakane

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

using namespace std;

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

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