剑指 Offer 56 – II. 数组中数字出现的次数 II

class Solution { 
   
public:
    int singleNumber(vector<int>& nums) { 
   
        vector<int>f(32,0);
        for(int i = 0;i < nums.size();i ++){ 
   
            int x = nums[i];
            for(int j = 0;j < 32;j ++){ 
   
                if(x >> j & 1)f[j] ++;
            }
        }
        for(int i = 0;i < 32;i ++){ 
   
            f[i] = f[i] % 3;
        }
        int res = 0;
        for(int i = 0;i < 32;i ++){ 
   
            if(f[i])res += 1 << i;
        }
        return res;
    }
};