Single Number
描述
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?
分析
异或，不仅能处理两次的情况，只要出现偶数次，都可以清零。
代码
// Single Number
// 时间复杂度O(n)，空间复杂度O(1)
class Solution {
public:
int singleNumber(vector<int>& nums) {
int x = 0;
for (int i : nums) {
x ^= i;
}
return x;
}
};