Find Common Characters

EasyArrays & Hashinghashing

Solve this the way you would in the interview: out loud, on a timer, with an AI interviewer asking follow-ups while you code. You get a scored report at the end.

Practice this as a mock interviewFree to start, no account needed

Problem

Given an array of lowercase strings words, find every character that appears in **all** of the words, keeping multiplicity: if a character appears at least k times in every word, it must appear k times in the answer. Return the result as an array of single-character strings sorted in **alphabetical order** (so repeated characters are adjacent).

Examples

Input: words = ["bella","label","roller"]
Output: ["e","l","l"]
Every word has at least one "e" and at least two "l"s.
Input: words = ["cool","lock","cook"]
Output: ["c","o"]
"o" appears only once in "lock", so it is kept once; "l" and "k" are missing from some word.

Constraints

  • 1 <= words.length <= 100
  • 1 <= words[i].length <= 100
  • `words[i]` consists of lowercase English letters

What the interviewer grades

A correct solution is one of five scores. The report also grades problem understanding (did you clarify inputs and edge cases before coding), problem solving, communication while you work, code quality, and testing. See a sample report, or read up on the pattern in the lessons.

More hashing problems