// Source : https://oj.leetcode.com/problems/single-number/

// Author : Hao Chen

// Date : 2014-06-17

/**********************************************************************************

*

* Given an array of integers, every element appears twice except for one. Find that single one.

*

* Note:

* Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory?

*

*

**********************************************************************************/

#include <stdio.h>

// This is classical interview question

// As we know, the same number XOR together will be 0,

// So, XOR all of numbers, the result is the number which only appears once.

int singleNumber(int A[], int n) {

int s = 0;

for(int i=0; i<n; i++){

s = s^A[i];

}

return s;

}

int main()

{

int a[]={1,1,2,2,3};

printf("%d\n", singleNumber(a,5));

return 0;

}