First non-repeating character using one traversal of string in C++

In this tutorial, we are going to learn how to find the first non-repeating character in the given string. Let's see an example.

Input −tutorialspoint

Output −u

Let's see the steps to solve the problem.

• Initialize the string.

• Initialize a map char and array to store the frequency of the characters in the string.

• Iterate over the string.

• Find the frequency of each character and store them in the map.

• Store the index of the character as well.

• Iterate over the character frequencies in the map.

• Print the first character with the frequency 1.

Example

Let's see the code.

#include <bits/stdc++.h> #include <map> using namespace std; void findDistinctCharacters(string random_string) {    // initializing char count    map<char, int[2]> chars;    // iterating over the string    for (int i = 0; i < random_string.size(); ++i){       chars[random_string[i]][0]++;       chars[random_string[i]][1] = i;    }    int char_index = INT_MAX;    // printing the first char with frequency 1    for (auto item: chars) {       // checking the frequency       if (item.second[0] == 1) {          char_index = min(char_index, item.second[1]);       }    }    // printing the first char with frequency 1    cout << random_string[char_index] << u; } int main() {    findDistinctCharacters("tutorialspoint");    return 0; }

Output

If you run the above code, then you will get the following result.

u

Conclusion

If you have any queries in the tutorial, mention them in the comment section.