Leetcode 1002. Find Common Characters

Problem statement

https://leetcode.com/problems/find-common-characters/

Solution

For every word create counter, then intersect all counters.

Complexity

It is O(n) for time, where n is total length of all words and O(max(26, m)) for space, where m is the length of answer.

Code

class Solution:
    def commonChars(self, A):
        lst = reduce(lambda x, y: x & y, list(map(lambda x: Counter(x), A)))
        ans = []
        for x, y in lst.items():
            ans += [x] * y
        return ans