Delete Duplicate Numbers in an Array using C

Let the user enter the numbers in an array, which contains duplicate elements.

Now, let’s write a code to delete the repeated numbers or elements in an array and make an array with unique elements without duplicates

For example,

An example is explained below −

• User input is 12, 30, 12, 45, 67, 30.
• Output is 12, 30, 45, 67 (after deleting duplicates).

Program

Following is the C program to delete the duplicate numbers in an array −

 Live Demo

#include <stdio.h>
#define MAX 100 // Maximum size of the array
int main(){
   int array[MAX]; // Declares an array of size 100
   int size;
   int i, j, k; // Loop variables
   /* Input size of the array */
   printf("enter the size of array : ");
   scanf("%d", &size);
   /* Input elements in the array */
   printf("Enter elements in an array : ");
   for(i=0; i<size; i++){
      scanf("%d", &array[i]);
   }
   /*find the duplicate elements in an array:
   for(i=0; i<size; i++){
      for(j=i+1; j<size; j++){
         /* If any duplicate found */
         if(array[i] == array[j]){
            /* Delete the current duplicate element */
            for(k=j; k<size; k++){
               array[k] = array[k + 1];
            }
            /* Decrement size after removing duplicate element */
            size--;
            /* If shifting of elements occur then don't increment j */
            j--;
         }
      }
   }
   printf("
Array elements after deleting duplicates : ");/*print an array after deleting the duplicate elements.
   for(i=0; i<size; i++){
      printf("%d\t", array[i]);
   }
   return 0;
}

Output

The output is as follows −

enter the size of array : 10
Enter elements in an array : 23 12 34 56 23 12 56 78 45 56
Array elements after deleting duplicates : 23 12 34 56 78 45