Single Number - leetcode

Single Number

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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?

思路：两个相同的数异或之后的值为零，那么该题将n个数异或，得到的就是那个single one~

class Solution {public:    int singleNumber(int A[], int n) {        // Note: The Solution object is instantiated only once and is reused by each test case.        if (A == 0 || n < 1)            return 0;        int key = A[0];        for (int i = 1; i < n; ++i) {            key ^= A[i];        }        return key;    }};