C Programming: Find the repeated character in a given string

Last update on August 06 2025 13:02:27 (UTC/GMT +8 hours)

32. Find Repeated Character

Write a C program to find the repeated character in a string.

Sample Solution:

C Code:

// Including the standard I/O library
#include<stdio.h>
#include<string.h>
// Function to check if a character exists in a string
int ifexists(char p, char q[], int v) {
    int i;
    for (i = 0; i < v; i++)
        if (q[i] == p) return (1); // If character exists, return 1
    return (0); // If character doesn't exist, return 0
}
int main() {
    char string1[80], string2[80]; // Declaration of string arrays
    int n, i, x; // Integer variables for iteration and length
    printf("Input a string: ");
    scanf("%s", string1); // Taking input string from the user
    n = strlen(string1); // Finding the length of the input string
    string2[0] = string1[0]; // Storing the first character of the input string in a new string array
    x = 1; // Initializing index for the new string as 1
    for (i = 1; i < n; i++) { // Loop through each character of the input string starting from index 1
        if (ifexists(string1[i], string2, x)) { // Check if the character exists in the new string
            printf("The first repetitive character in %s is: %c ", string1, string1[i]); // Print the first repetitive character
            break; // Exit the loop
        } else {
            string2[x] = string1[i]; // Add the character to the new string array
            x++; // Increment the index of the new string array
        }
    }
    if (i == n)
        printf("There is no repetitive character in the string %s.", string1); // If no repetitive character found in the input string
}

Output:

 Input a string: The first repetitive character in w3resource is: r

Flowchart:

Flowchart: Find the repeated characte in a given string

For more Practice: Solve these Related Problems:

Write a C program to detect and print the first repeated character in a string using nested loops.
Write a C program to find all characters that occur more than once in a string and display their positions.
Write a C program to determine the first character that repeats in a string by comparing each character with the rest.
Write a C program to identify repeated characters and print each with the number of times it appears.

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