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 .
Find Duplicates Characters

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.
Find Duplicates Characters

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
Software Engineering SDLC