#Leetcode# 137. Single Number II

https://leetcode.com/problems/single-number-ii/

Given a non-empty array of integers, every element appears three times except for one, which appears exactly once. Find that single one.

Note:

Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory?

Example 1:

Input: [2,2,3,2]
Output: 3

Example 2:

Input: [0,1,0,1,0,1,99]
Output: 99

代码：

class Solution {
public:
    int singleNumber(vector<int>& nums) {
        int n = nums.size();
        map<int, int> mp;
        for(int i = 0; i < n; i ++)
            mp[nums[i]] ++;
        for(int i = 0; i < n; i ++)
            if(mp[nums[i]] == 1)
                return nums[i];
    }
};