Case-Sensitive Word Mismatch Function

MediumPython

Problem

A Meta Ads text-processing pipeline compares two whitespace-delimited strings and needs to identify word occurrences that cannot be matched between them. Write a function that returns the unmatched occurrences, preserving their left-to-right order within their original string.

Matching is case sensitive. If a word occurs a times in the first string and b times in the second, return abs(a - b) copies of that word from the string with the larger count. Preserve the order in which returned copies appear in that source string. Punctuation remains part of a word because words are split only on whitespace.

Formal Specification

Implement unmatched_words(s1, s2).

Input: Two strings, s1 and s2, containing zero or more whitespace-delimited words.
Output: A list of strings containing unmatched word occurrences. Return an empty list when every occurrence can be paired.

Constraints

0 <= len(s1), len(s2) <= 10^5
Each string contains at most 2 * 10^4 words
Words are separated by arbitrary whitespace
Matching is case sensitive
Punctuation remains part of a word

Function Signature

def unmatched_words(s1, s2):

Formal Specification

Implement unmatched_words(s1, s2).

Input: Two strings, s1 and s2, containing zero or more whitespace-delimited words.
Output: A list of strings containing unmatched word occurrences. Return an empty list when every occurrence can be paired.