137_Single_Number_II.cc

class Solution {
public:
    int singleNumber(vector<int>& nums) {
        if(nums.size()<4)   return nums[0];
        sort(nums.begin(),nums.end());
        for(int i=0;i<nums.size()-2;++++++i){
            if(nums[i]!=nums[i+2]) return nums[i];
        }
        return nums[nums.size()-1];
    }
};