Leetcode|136. Single Number

【问题描述】

Given a non-empty 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?

Example 1:

Input: [2,2,1]
Output: 1

Example 2:

Input: [4,1,2,1,2]
Output: 4

【解题思路】

思路一：暴力解法，对于每一个数字遍历vector，两重循环，时间复杂度n^2（(⊙o⊙)…放弃！）

思路二：运用异或操作，0+a=a,a+b=b+a，eg: 对于[4,1,2,1,2]，可以认为是[1,1,2,2,4]，最后的结果就是4

class Solution {
public:
    int singleNumber(vector<int>& nums) {
        int result=0;
        for(int i=0;i<nums.size();i++){
            result=result^nums[i];
        }
        return result;   
    }
};