136. Single Number

Question:

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:

Logic: XOR will return 1 only on two different bits. So if two numbers are the same, XOR will return 0. Finally only one number left.

A ^ A = 0 and A ^ B ^ A = B.

class Solution {
    public:
        int singleNumber(int A[], int n) {
            int result=A[0];
            for(int i=1;i<n;i++)
            {
                result= result^A[i];  /* Get the xor of all elements */
            }
            return result;
        }
};

题目直达：https://leetcode.com/problems/single-number/#/solutions