動機

就是算

Problem

Write an algorithm to determine if a number n 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.
  • 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.

Return true if n is a happy number, and false if not.

 

Example 1:

Input: n = 19Output: trueExplanation:12 + 92 = 8282 + 22 = 6862 + 82 = 10012 + 02 + 02 = 1

Example 2:

Input: n = 2Output: false

 

Constraints:

  • 1 <= n <= 231 - 1

Sol

def happy(n):
    tmp = [int(x)*int(x) for x in list(str(n))]
    return sum(tmp)
class Solution:
    def isHappy(self, n: int) -> bool:
        tbl = set()
        while n not in tbl and n != 1:
            tbl.add(n)
            n = happy(n)
        return (n == 1)