1399-Count-Largest-Group.py

'''
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