Happy Number
Created: April 2, 2002 by [lek-tin]
Last updated: April 2, 2002
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 (int to str)
class Solution:
def isHappy(self, n):
"""
:type n: int
:rtype: bool
"""
tried = set()
currentNum = n
while currentNum not in tried:
tried.add(currentNum)
sum = 0
for num in [int(d) for d in str(currentNum)]:
sum += num**2
if sum == 1:
return True
currentNum = sum
return False
Solution (mod operation)
class Solution:
def isHappy(self, n: int) -> bool:
tried = set()
while True:
newN = 0
while n:
temp = n % 10
n //= 10
newN += temp * temp
if newN == 1:
return True
if newN in tried:
return False
tried.add(newN)
n = newN