C program to print all unique elements in array

Write a C program to input elements in array and print all unique elements in array. How to find unique elements in array in C programming. Logic to find unique elements in array in C program.

Input array elements: 1, 2, 3, 5, 1, 5, 20, 2, 12, 10

All unique elements in the array are: 3, 20, 12, 10

Required knowledge

Basic Input Output, For loop, Array

Logic to find unique elements in array

Step by step descriptive logic to find unique elements in array.

1. Input size and elements in array. Store it in some variable say size and arr.
2. Find frequency of each element and store it in an array say freq.
3. Print array elements with frequency 1 which is our required unique elements.

Program to print unique elements in array

/**
 * C program to print all unique elements in array
 */

#include <stdio.h>
#define MAX_SIZE 100

int main()
{
    int arr[MAX_SIZE], freq[MAX_SIZE];
    int size, i, j, count;
 
    /* Input size of array and elements in array */
    printf("Enter size of array: ");
    scanf("%d", &size);
    printf("Enter elements in array: ");
    for(i=0; i<size; i++)
    {
        scanf("%d", &arr[i]);
        freq[i] = -1;
    }
 
    /* Find frequency of each element */
    for(i=0; i<size; i++)
    {
        count = 1;
        for(j=i+1; j<size; j++)
        {
            if(arr[i] == arr[j])
            {
                count++;
                freq[j] = 0;
            }
        }
 
        if(freq[i] != 0)
        {
            freq[i] = count;
        }
    }
 
    /* Print all unique elements of array */
    printf("\nUnique elements in the array are: ");
    for(i=0; i<size; i++)
    {
        if(freq[i] == 1)
        {
            printf("%d ", arr[i]);
        }
    }

    return 0;
}

Enter size of array: 10
Enter elements in array: 1 2 3 5 1 5 20 2 12 10

Unique elements in the array are: 3 20 12 10

Happy coding 😉