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202. Happy Number

Hash Table Math Two Pointers

Problem - Happy Number

Easy

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 = 19
Output: true
Explanation:
12 + 92 = 82
82 + 22 = 68
62 + 82 = 100
12 + 02 + 02 = 1

Example 2:

Input: n = 2
Output: false

 

Constraints:

  • 1 <= n <= 231 - 1

Solutions

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class Solution:
    def isHappy(self, n: int) -> bool:
        visited = set()
        while n != 1 and n not in visited:
            visited.add(n)
            val = 0
            while n:
                n, remain = divmod(n, 10)
                val += remain ** 2
            n = val

        return n == 1

Submission Stats:

  • Runtime: 0 ms (100.00%)
  • Memory: 18 MB (18.04%)