2306. Naming a Company

https://leetcode.com/problems/naming-a-company/

Python

from collections import defaultdict
from string import ascii_lowercase


class Solution:
    def distinctNames(self, ideas: List[str]) -> int:
        mapper = defaultdict(set)
        for idea in ideas:
            mapper[idea[0]].add(idea[1:])

        ans = 0
        for i in range(25):
            for j in range(i+1, 26):
                prefix1 = ascii_lowercase[i]
                prefix2 = ascii_lowercase[j]

                mutuals = len(mapper[prefix1] & mapper[prefix2])

                ans += 2 * (len(mapper[prefix1]) - mutuals) * (len(mapper[prefix2]) - mutuals)

        return ans