【LEETCODE】202-Happy Number

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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

用哈希表记录每个出现过的sum，

当sum不是1并且再次出现的时候，说明进入循环，则返回false

当sum是1的时候，则返回true

class Solution(object):    def isHappy(self, n):        """        :type n: int        :rtype: bool        """                t=set()                          #定义一个哈希表                while n!=1 and n not in t:       #当n是1时，说明是happy，返回true，当n在t但不是1时，说明循环，返回false                        t.add(n)                     #将n加入哈希表里                        s=0                        while n!=0:                                a=n%10                s+=a*a                   #对每一位的数求平方，再加和                n=int(n/10)                        n=s                          #n变成最后的和s                return n==1                                            #if s not in t.key():                #t.add(s)                #n=s            #else:                #return False

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