【LeetCode】202. Happy Number

標籤：

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

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

 

迴圈計算每位元字的平方和，直到出現結果為1(返回true)或者重複(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;    }};

【LeetCode】202. Happy Number