LeetCode----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

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

分析：

按照给定的流程编写逻辑，使用集合判断当然判断的数是否出现了循环。

Python代码：

class Solution(object):    def isHappy(self, n):        """        :type n: int        :rtype: bool        """        n_map = {}        for i in range(10):            n_map[i] = pow(i, 2)        n_set = set()        while True:            if n == 1:                return True            if n in n_set:                return False            else:                n_set.add(n)            res = self.decoden(n)            n = 0            for i in res:                if i in n_map:                    n += n_map[i]                else:                    n += i    def decoden(self, n):        res = []        while n / 10:            res.append(n % 10)            n = n / 10        return res + [n]

更简便的C++代码：

class Solution {public:    bool isHappy(int n) {        set<int> n_set;        int m = 0;        while(true){            while(n){                m = m + (n % 10) * (n % 10);                n = n / 10;            }            if(m == 1){                return true;            }            if(n_set.find(m) != n_set.end()){                return false;            }else{                n_set.insert(m);            }            n = m;            m = 0;        }    }};