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。