ItemAppearOnce.cpp

// ItemAppearOnce.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"

#define INT_SIZE 32

int getSingle(int arr[], int n)
{
	int result = 0; 

	int x, sum; 

	// Iterate through every bit
	for(int i=0; i< INT_SIZE; i++)
	{
		// Find sum of set bits at ith position in all array elements
		sum = 0; 
		x = (1<<i); 

		for(int j=0;j<n;j++)
		{
			if(arr[j] & x) 
				sum++; 
		}

		// The bits with sum not multiple of 3, are the
        // bits of element with single occurrence.
		if(sum%3)
			result |=x; 
	}

	return result; 

}

int _tmain(int argc, _TCHAR* argv[])
{

	int arr[] = {12, 1, 12, 3, 12, 1, 1, 2, 3, 2, 2, 3, 7};

    int n = sizeof(arr) / sizeof(arr[0]);

    printf("The element with single occurrence is %d ",
            getSingle(arr, n));
    
	return 0;
}