class  {
public:
    int singleNumber (vector<int>& nums) {
        int result = 0;
        for (int num : nums) {
            result ^= num;
        }
        return result;
    }
};

class  {
public:
    vector<int> intersection(vector<int>& nums1, vector<int>& nums2) {
        unordered_set<int> myset(nums1.begin(), nums1.end());
        vector<int> result;
        for (int num2 : nums2) {
            if (myset.count(num2) > 0) {
                result.push_back(num2);
                myset.erase(num2);
            }
        }
        return result;
    }
};

class  {
public:
    unordered_map<int, int> path;
    bool isHappy(int n) {
        int value=0;
        int key=n;
        while (n) {//calculate the value of the key.
            int temp = n%10;
            value+=temp*temp;
            n/=10;
        }
        if (value==1) {//if the value is 1,the key is a happy number.
            return true;
        }
        if (path.count(value) > 0) {//if the value is already in the map,there is a cycle,so the key is not a happy number.
            return false;
        }
        path[key]=value;//put the key/value in the map
        return isHappy(value);//calculate recursively
    }
};