LeetCode

Single Number

2014.1.13 20:17

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?

Solution:

　　Exclusive OR is a wonderful operator.

　　Time complexity is O(n), space complexity is O(1).

Accepted 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 res = 0;

        for(int i = 0; i < n; ++i){
            res ^= A[i];
        }

        return res;
    }
};