Description
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:
Input: 19
Output: true
Explanation:
12 + 92 = 82
82 + 22 = 68
62 + 82 = 100
12 + 02 + 02 = 1
描述
一个“快乐数”定义为：对于一个正整数，每一次将该数替换为它每个位置上的数字的平方和，然后重复这个过程直到这个数变为 1，也可能是无限循环但始终变不到 1。如果可以变为 1，那么这个数就是快乐数。
示例:
输入: 19
输出: true
解释:
12 + 92 = 82
82 + 22 = 68
62 + 82 = 100
12 + 02 + 02 = 1
思路
- 两个辅助函数:divide函数将所有的一个数拆成单独的数字；square求所有数字的平方和.
- 我们用一个hash set 来记录已经出现过的结果，如果有一个结果已经出现过且不等于1返回Fasle，如果出现了1返回True.
# -*- coding: utf-8 -*- # @Author: 何睿 # @Create Date: 2019-01-20 21:06:07 # @Last Modified by: 何睿 # @Last Modified time: 2019-01-21 18:50:47 class Solution: def isHappy(self, n): """ :type n: int :rtype: bool """ numset = set() newn = self.square(self.divide(n)) # 如果求和的结果没有出现过 while newn not in numset: numset.add(newn) newn = self.square(self.divide(newn)) # 如果等于1，返回True if newn == 1: return True # 若求和的结果已经出现且不等于1，返回False return False # 拆分函数，返回list def divide(self, n): res = [] while n: res.append(n % 10) n //= 10 return res # 返回所有数子的平方和 def square(self, nums): return sum([x**2 for x in nums])
源代码文件在这里.
