C Program to Count Total Duplicate Elements in an Array

How to write a C Program to Count Total Duplicate Elements in an Array?. Before counting duplicate elements in an array, please refer to Array in C article to know the Array size, index position, etc.

C Program to Count Total Duplicate Elements in an Array Example

This program asks the user to enter Array Size and array elements. Next, it is going to count the total number of duplicate elements present in this array using For Loop.

/* C Program to Count Total Duplicate Elements in an Array */
 
#include <stdio.h>
 
int main()
{
	int arr[10], i, j, Size, Count = 0;
	
	printf("\n Please Enter Number of elements in an array  :   ");
	scanf("%d", &Size);
	
	printf("\n Please Enter %d elements of an Array  :  ", Size);
	for (i = 0; i < Size; i++)
	{
    	scanf("%d", &arr[i]);
   	}     
 
	for (i = 0; i < Size; i++)
	{
		for(j = i + 1; j < Size; j++)
		{
    		if(arr[i] == arr[j])
    		{
    			Count++;
				break;
			}
		}
	}

 	printf("\n Total Number of Duplicate Elements in this Array  =  %d ", Count);
	     
 	return 0;
}

In this Program, We declared 1 One Dimensional Arrays arr[] of size 10 and also declared i to iterate the Array elements. The below printf statement asks the User to enter the array arr[] size (Number of elements an Array can hold). And, scanf statement will assign the user entered values to Size variable.

printf("\n Please Enter Number of elements in an array  :   ");
scanf("%d", &Size);

Below For loop will help to iterate each cell present in the arr[5] array. Condition (i < Size) in the for loop ensure that the compiler to not exceed the array limit. The C Programming scanf statement inside the for loop will store the user entered values in every individual array element such as arr[0], arr[1], arr[2], arr[3], arr[4]

for (i = 0; i < Size; i++)
{
    	scanf("%d", &arr[i]);
}

In the next line, We have one more for loop. It is to iterate each element in an array. If Statement to check for the duplicates

for (i = 0; i < Size; i++)
{
	for(j = i + 1; j < Size; j++)
	{
   		if(arr[i] == arr[j])
   		{
  			Count++;
			break;
		}
	}
}

User inserted values are: a[5] = {10, 20, 10, 30, 20}

First For Loop – First Iteration: for(i = 0; i < 5; 0++)
The condition (0 < 5) is True.

Second For Loop – First Iteration: for(j = 0 + 1; 1 < 5; 1++)
The condition (1 < 5) is True. So, it will start executing the statements inside the loop
if(arr[i] == arr[j])
if(10 == 20) – Condition is False

Second For Loop – Second Iteration: for(j = 2; 2 < 5; 2++)
The condition (2 < 5) is True. So, it will start executing the statements inside the loop
if(arr[i] == arr[j])
if(10 == 10) – Condition is True

The count will increment to 1. Do the same for remaining iterations.

C Program to Count Total Duplicate Elements in an Array Example 2

This program to count duplicate array elements is same as above, but this time we separated the logic using Functions concept.

/* C Program to Count Total Duplicate Elements in an Array */
 
#include <stdio.h>

int Total_Duplicates(int arr[], int Size);
 
int main()
{
	int arr[10], i, Size, Count = 0;
	
	printf("\n Please Enter Number of elements in an array  :   ");
	scanf("%d", &Size);
	
	printf("\n Please Enter %d elements of an Array  :  ", Size);
	for (i = 0; i < Size; i++)
	{
    	scanf("%d", &arr[i]);
   	}     
 
	Count = Total_Duplicates(arr, Size);

 	printf("\n Total Number of Duplicate Elements in this Array  =  %d ", Count);
	     
 	return 0;
}
int Total_Duplicates(int arr[], int Size)
{
	int i, j, Count = 0;
	
	for (i = 0; i < Size; i++)
	{
		for(j = i + 1; j < Size; j++)
		{
    		if(arr[i] == arr[j])
    		{
    			Count++;
				break;
			}
		}
	}
	return Count;	
}

Please Enter Number of elements in an array  :   10

 Please Enter 10 elements of an Array  :  1 2 3 4 1 2 5 6 5 9

 Total Number of Duplicate Elements in this Array  =  3