202. Happy Number

Write an algorithm to determine if a number is "happy".

A happy number is a number defined by the following process: Starting with any positive integer, replace the number by the sum of the squares of its digits, and repeat the process until the number equals 1 (where it will stay), or it loops endlessly in a cycle which does not include 1. Those numbers for which this process ends in 1 are happy numbers.

Example: 19 is a happy number

• 1² + 9² = 82
• 8² + 2² = 68
• 6² + 8² = 100
• 1² + 0² + 0² = 1

//存储每次计算的结果，如果出现重复那么结果为false.

class Solution {
public:
    bool isHappy(int n) {
        unordered_map<int, bool> map;
    
        int sum = calSum(n);
        while (sum != 1) {
            if (map[sum] == true)
                return false;
            map[sum] = true;
            sum = calSum(sum);
        }
        return true;
    }
    
    int calSum(int n) {
        int res = 0;
        while (n) {
            int num = n % 10;
            n /= 10;
            res += num*num;
        }
        return res;
    }

};