C Exercises: Count the total number of duplicate elements in an array

Last update on January 17 2025 13:20:23 (UTC/GMT +8 hours)

Write a program in C to count the total number of duplicate elements in an array.

The task involves writing a C program to count the number of duplicate elements in an array. The program will take a specified number of integer inputs, store them in an array, and then determine and display how many elements appear more than once.

Visual Presentation:

Pseudo code to count the total number of duplicate elements in an array:

• Initialize a variable 'count' to 0.
• Read the array size, 'n'.
• Declare an integer array of size 'n'.
• Read the array elements.
• Loop through each element of the array from index 0 to n-2: a. Loop through the remaining elements of the array from index i+1 to n-1: i. If the current element and any of the remaining elements are equal, increment the 'count' variable and break out of the inner loop.
• Print the value of 'count' as the total number of duplicate elements in the array.
• End

Sample Solution:

C Code:

#include <stdio.h>
// Main function
int main()
{
    int arr[100];  // Declare an array of size 100 to store integer values
    int n, mm = 1, ctr = 0;  // Declare variables to store array size, mm (unused), and duplicate counter
    int i, j;  // Declare loop counters
    // Prompt the user to input the number of elements to be stored in the array
    printf("Input the number of elements to be stored in the array :");
    scanf("%d", &n);
    // Prompt the user to input n elements into the array
    printf("Input %d elements in the array :\n", n);
    for (i = 0; i < n; i++)
    {
        printf("element - %d : ", i);
        scanf("%d", &arr[i]);  // Read the input and store it in the array
    }
    // Check for duplicate elements in the array using nested loops
    for (i = 0; i < n; i++)
    {
        for (j = i + 1; j < n; j++)
        {
            if (arr[i] == arr[j])
            {
                ctr++;  // Increment the duplicate counter if a duplicate is found
                break;  // Exit the inner loop as soon as a duplicate is found
            }
        }
    }
    // Display the total number of duplicate elements found in the array
    printf("Total number of duplicate elements found in the array: %d\n", ctr);
    return 0;  // Return 0 to indicate successful execution
}

Sample Output:

Input the number of elements to be stored in the array :5
Input 5 elements in the array :
element - 0 : 1
element - 1 : 1
element - 2 : 2
element - 3 : 3
element - 4 : 3
Total number of duplicate elements found in the array: 2

Flowchart:

C Programming Code Editor:

Click to Open Editor

Previous: Write a program in C to copy the elements one array into another array.
Next: Write a program in C to print all unique elements in an array.