[LeetCode]#1002. Find Common Characters

Fatboy Slim
1 min readJan 18, 2021


Environment: Python 3.8

Key technique: Counter

Given an array A of strings made only from lowercase letters, return a list of all characters that show up in all strings within the list (including duplicates). For example, if a character occurs 3 times in all strings but not 4 times, you need to include that character three times in the final answer.

You may return the answer in any order.

Example 1:

Input: ["bella","label","roller"]
Output: ["e","l","l"]

Example 2:

Input: ["cool","lock","cook"]
Output: ["c","o"]


  1. Use Counter for counting A[0] string.
  2. Check c &= A[1] result
  3. Check c &= A[2] result
  4. Return result


from collections import Counter
class Solution:
def commonChars(self, A):
if not A:
return None

c = Counter(A[0])
for word in A[1:]:
c &= Counter(word)

ans = []
for x in c:
ans += [x] * c[x]
return ans






Fatboy Slim

Interesting in any computer science.