137. Single Number II

//37ms class Solution {public:    int singleNumber(vector<int>& nums) {        int result=0;        int k=1;        for(int i=0;i<32;i++)        {            int j=0;            for(auto a=nums.begin();a!=nums.end();a++)            {                if(*a&k) j++;            }            result|=((j%3)*k);            k=k<<1;        }        return result;    }};//20msclass Solution {public:    int singleNumber(vector<int>& nums) {        if(nums.size()==1) return nums[0];        //if(nums.size()==0) return NULL;        sort(nums.begin(),nums.end());        if(nums[0]!=nums[1]) return nums[0];        if(*(nums.end()-1)!=*(nums.end()-2)) return *(nums.end()-1);        for(auto a=nums.begin()+1;a!=nums.end()-1;a++)        {            if(*a!=*(a+1)&&*a!=*(a-1)) return *a;        }    }};