C program to find number of duplicate elements in an array

In this article we will learn to implement a C program to find number of duplicate elements in an array. A C program is provided below which reads a list of number and prints the number of duplicates in a given array.

Note: This program only works if the numbers are repeated for 2 times. It doesn’t work if the numbers are repeated more than 2 times.

The program is as follows:

#include <stdio.h>
#include <conio.h>

int main() 
{
	int n;
	printf("Enter n: ");
	scanf("%d", &n);
	int a[20];
	printf("Enter array elements: ");
	for(int i = 0; i < n; i++)
		scanf("%d", &a[i]);
	int temp;
	//Sorting the array
	for(int i = 0; i < n - 1; i++)
	{
		for(int j = i+1; j < n; j++)
		{
			if(a[i] > a[j])
			{
				temp = a[i];
				a[i] = a[j];
				a[j] = temp;
			}
		}
	}
	int count = 0;
	for(int i = 0; i < n - 1; i++)
	{
		if(a[i] == a[i+1])
			count++;
	}
	printf("No. of duplicates: %d", count);
	getch();
    return 0;
}

Input and output for the above program is as follows:

Enter n: 10
Enter array elements: 1 2 1 3 2 4 4 5 3 6
No. of duplicates: 4

Suryateja Pericherla

Suryateja Pericherla, at present is a Research Scholar (full-time Ph.D.) in the Dept. of Computer Science & Systems Engineering at Andhra University, Visakhapatnam. Previously worked as an Associate Professor in the Dept. of CSE at Vishnu Institute of Technology, India.

He has 11+ years of teaching experience and is an individual researcher whose research interests are Cloud Computing, Internet of Things, Computer Security, Network Security and Blockchain.

He is a member of professional societies like IEEE, ACM, CSI and ISCA. He published several research papers which are indexed by SCIE, WoS, Scopus, Springer and others.