Search Mysterious Grid

Problem Overview

• Count how many target symbols from a set appear in a character grid under strict path rules.
• Input: a 2D char grid and a list of unique symbols; Output: total valid occurrences.
• A match uses adjacent cells, starting anywhere, moving initially left-to-right or top-to-bottom, with at most one reversal.
• Real-world theme: searching ancient symbols in a mysterious grid.
• From Meta interviews; a coding interview problem and interview question.