leetcode202

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202. Happy Number

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:

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Input: 19
Output: true
Explanation: 
1^2 + 9^2 = 82
8^2 + 2^2 = 68
6^2 + 8^2 = 100
1^2 + 0^2 + 0^2 = 1

Idea

Since, there will be a repeated loop. We can use set() to save the repeated numbers.

Code

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class Solution(object):
    def isHappy(self, n):
        """
        :type n: int
        :rtype: bool
        """
        set_ = set()
        while n not in set_:
            set_.add(n)
            tmp = 0
            while n > 0:
                bit = n % 10
                tmp += bit * bit
                n /= 10
            n = tmp
            
        return 1 in set_