class Solution {
public:
    bool isHappy(int n) {
        int sum = 0;
        unordered_set<int> sumSet;

        while(1){
            sum = 0;
            while(n > 0){
                int digit = n % 10;
                sum += (digit * digit);
                n /= 10;
            }

            if(sum == 1) return true;

            if(sumSet.find(sum) != sumSet.end()) return false;
            else  sumSet.insert(sum);

            n = sum;
        }

        return false;
    }
};

class Solution {
public:
    unordered_set<int> sumSet;

    int getNext(int num){
        int sum = 0;

        while(num > 0){
            int digit = num % 10;
            sum += (digit * digit);
            num /= 10;
        }

        return sum;
    }
    bool isHappy(int n) {
        
        while(n != 1 && sumSet.find(n) == sumSet.end()){
            sumSet.insert(n);
            n = getNext(n);
        }

        return n == 1;
    }
};

class Solution {
public:

    int getNext(int num){
        int sum = 0;

        while(num > 0){
            int digit = num % 10;
            sum += (digit * digit);
            num /= 10;
        }

        return sum;
    }

    bool isHappy(int n) {
        int slow = n;
        int fast = getNext(n);

        while(fast != 1 && fast != slow){
            slow = getNext(slow);
            fast = getNext(getNext(fast));
        }

        return fast == 1;
    }
};