first repeating character in a string code example

Example 1: first repeating character in a string

// C# program to find the first
// repeated character in a string
using System;
using System.Collections.Generic;
 
class GFG
{
// This function prints the first
// repeated character in str[]
public static char firstRepeating(char[] str)
{
    // Creates an empty hashset
    HashSet<char> h = new HashSet<char>();
 
    // Traverse the input array
    // from left to right
    for (int i = 0; i <= str.Length - 1; i++)
    {
        char c = str[i];
 
        // If element is already in hash set,
        // update x and then break
        if (h.Contains(c))
        {
            return c;
        }
 
        else // Else add element to hash set
        {
            h.Add(c);
        }
    }
 
    return '\0';
}
 
// Driver Code
public static void Main(string[] args)
{
    string str = "geeksforgeeks";
    char[] arr = str.ToCharArray();
    Console.WriteLine(firstRepeating(arr));
}
}

Example 2: first repeating character in a string

// CPP program to find the first
// repeated character in a string
#include <bits/stdc++.h>
using namespace std;
 
// Returns first repeating character in str.
char firstRepeating(string &str)
{
    // Creates an empty hashset
    unordered_set<char> h;
 
    // Traverse the input array from left to right
    for (int i=0; i<str.length(); i++)
    {
        char c = str[i];
 
        // If element is already in hash set, update x
        // and then break
        if (h.find(c) != h.end())
            return c;
 
        else // Else add element to hash set
            h.insert(c);
    }
 
    // If there was no repeated character
    return '\0';
}
 
// Driver method to test above method
int main ()
{
    string str = "geeksforgeeks";
    cout << firstRepeating(str);
    return 0;
}