leetcode之137. Single Number II（C++解法 哈希表计数）

题目：
Given an array of integers, every element appears three times except for one. Find that single one.

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

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class Solution {
public:
    int singleNumber(vector<int>& nums) {
           multimap<int,int> coun;
        for(int i=0;i<nums.size();i++)
        {
            coun.insert({nums[i],i});
        }
        int j=0;
        for(;j<nums.size();j++)
        {
            if(coun.count(nums[j])!=3)
            break;
        }
        return nums[j];
    }

}

只上一个用这种解法是一样的，不过需要额外的空间。