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
class Solution:
def isHappy(self, n: int) -> bool:
# hashset = set()
# while n != 1:
# # s = list(map(int, str(n)))
# # n = 0
# # for num in s:
# # n += num*num
# total = 0
# while n//10 != 0:
# total += (n%10)**2
# n = n// 10
# n = n*n + total
# if n in hashset:
# return False
# else:
# hashset.add(n)
# return True
def get_next(n):
total = 0
while n > 0:
n, digit = divmod(n, 10)
total += digit**2
return total
slow = n
fast = get_next(n)
while fast!=1 and fast!=slow:
slow = get_next(slow)
fast = get_next(get_next(fast))
return fast == 1