1399-count-largest-group.py

"""
Problem Link: https://leetcode.com/problems/count-largest-group/

Given an integer n. Each number from 1 to n is grouped according to the sum of its digits. 
Return how many groups have the largest size.

Example 1:
Input: n = 13
Output: 4
Explanation: There are 9 groups in total, they are grouped according sum of its digits of 
numbers from 1 to 13:
[1,10], [2,11], [3,12], [4,13], [5], [6], [7], [8], [9]. There are 4 groups with largest size.

Example 2:
Input: n = 2
Output: 2
Explanation: There are 2 groups [1], [2] of size 1.

Example 3:
Input: n = 15
Output: 6

Example 4:
Input: n = 24
Output: 5
 
Constraints:
1 <= n <= 10^4
"""
class Solution:
    def countLargestGroup(self, n: int) -> int:
        d = {}
        max_value = count = 0
        for number in range(1,n+1):
          num_sum = self.number_sum(number)
          d[num_sum] = d.get(num_sum, 0) + 1
          
          if d[num_sum] > max_value:
            count = 0
            max_value = d[num_sum]
            
          if d[num_sum] == max_value:
            count += 1
        return count
            
            
    def number_sum(self, n):
      num_sum = 0
      while n:
        num_sum += n % 10
        n //= 10
      return num_sum