C Program To Find Duplicate characters in a string

May 13, 2022

Find Duplicate characters in a string

Today in this article we will discuss how to Find Duplicate characters in a string and we will be using C programming language. We will also disscuss various methods to do the porblem .

Algorithm

Define a string and take the string as input form the user.
Two loops will be used to find the duplicate characters. Outer loop will be used to select a character and then initialize variable count by 1 its inside the outer loop so that the count is updated to 1 for every new character.
Inner loop will compare the selected character with the rest of the characters present in the string.
If a match is found, it increases the count by 1 and set the duplicates of selected characters by ‘0’ to mark them as visited.
After the inner loop, if the count of characters is greater than 1, then it has duplicates in the string.

C Code :-

Run

#include <stdio.h> 
#include <string.h> 
int main() 
{ 
  char string[100]; 
  int count; 
  printf("Enter the string : \n"); 
  scanf("%[^\n]*c",string);

  printf("Duplicate characters in a given string: \n"); 

  //Counts each character present in the string 
  for(int i = 0; i < strlen(string); i++) { 
  count = 1; //Updates thecount again to 1 for every new character

  for(int j = i+1; j < strlen(string); j++) { 
      if(string[i] == string[j] && string[i] != ' ') { 
    count++; 
   //Set string[j] to 0 to avoid printing visited character 
   string[j] = '0'; 
  } 
 } 

  //A character is considered as duplicate if count is greater than 1 

 if(count > 1 && string[i] != '0') 
 printf("%c\n", string[i]); 
  } 

 return 0; 
}

Output:-

Enter the string : 
prakriti vedi
Duplicate characters in a given string: 
r
i

Enter the string : 
ritika singh
Duplicate characters in a given string: 
i

Enter the string :
Aishwariya prasad 
Duplicate characters in a given string: 
i
s
a
r