Single Number [LEETCODE]

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?

 

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Remember this property of XOR:

a ^ a = 0

0 ^ b =b

So all we need is to calculate XOR result in given array one by one.

Here's the code:

class Solution {
public:
    int singleNumber(int A[], int n) {
        // Note: The Solution object is instantiated only once and is reused by each test case.
        int result = 0;
        for (int i = 0; i < n ; i++) {
            result = result^A[i];
        }
        return result;
        
    }
};