LeetCode： Find Common Characters

Question

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"]

Solution

def common_chars(a)
  a.first.chars.uniq.map { |char|
    [char] * (a.map { |str| str.count(char) }.min)
  }.flatten
end