Leetcode/problem202.py at master · Yuchen112211/Leetcode · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
'''

202. Happy Number
Easy

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

Solution:
Use set to record the appeared number.

'''
class Solution(object):
    def isHappy(self, n):
        """
        :type n: int
        :rtype: bool
        """
        if n == 0:
        	return False
        if n == 1:
        	return True
        appeared = set([n])
        while n != 1:
        	digits = str(n)
        	nextNum = 0
        	for i in digits:
        		nextNum += int(i) * int(i)
        	if nextNum in appeared:
        		return False
        	appeared.add(nextNum)
        	n = nextNum
        return True


s = Solution()
print s.isHappy(20)