【LeetCode】202. Happy Number

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

• 1^2 + 9^2 = 82
• 8^2 + 2^2 = 68
• 6^2 + 8^2 = 100
• 1^2 + 0^2 + 0^2 = 1

Credits:
Special thanks to @mithmatt and @ts for adding this problem and creating all test cases.

 

循环计算每位数字的平方和，直到出现结果为1(返回true)或者重复(返回false)

class Solution {
public:
    bool isHappy(int n) {
        unordered_map<int, bool> m;
        int sum = Helper(n);
        while(sum != 1)
        {
            if(m[sum] == true)
                return false;
            m[sum] = true;
            sum = Helper(sum);
        }
        return true;
    }
    int Helper(int n)
    {// sum of the squares of its digits
        int ret = 0;
        while(n)
        {
            int digit = n%10;
            n /= 10;
            ret += (digit*digit);
        }
        return ret;
    }
};