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This question evaluates a candidate's skills in backtracking search, grid traversal, and managing state for constrained path-finding problems. Commonly asked to assess algorithmic problem-solving, recursion and memory-management (including in-place visited marking) within the Coding & Algorithms domain, it emphasizes practical application and understanding of time and space complexity trade-offs rather than purely theoretical concepts.

  • medium
  • Turo
  • Coding & Algorithms
  • Software Engineer

Check if a word exists in a grid

Company: Turo

Role: Software Engineer

Category: Coding & Algorithms

Difficulty: medium

Interview Round: Technical Screen

Given an m×n grid of characters and a string word, determine whether the word can be formed by sequentially adjacent cells (adjacent means horizontally or vertically). The same cell may not be used more than once in a single path. Implement a function `exists(board, word) -> bool`. Follow-up: Explain how to do the visited marking in-place (without an extra visited matrix) and derive the time and space complexity.

Quick Answer: This question evaluates a candidate's skills in backtracking search, grid traversal, and managing state for constrained path-finding problems. Commonly asked to assess algorithmic problem-solving, recursion and memory-management (including in-place visited marking) within the Coding & Algorithms domain, it emphasizes practical application and understanding of time and space complexity trade-offs rather than purely theoretical concepts.

Return whether word can be traced through adjacent cells without reusing a cell.

Examples

Input: ([['A', 'B', 'C', 'E'], ['S', 'F', 'C', 'S'], ['A', 'D', 'E', 'E']], 'ABCCED')

Expected Output: True

Explanation: Classic true.

Input: ([['A', 'B'], ['C', 'D']], 'ABCD')

Expected Output: False

Explanation: No diagonal jump.

Input: ([['A']], 'AA')

Expected Output: False

Explanation: Cannot reuse cell.

Input: ([], '')

Expected Output: True

Explanation: Empty word.

Last updated: Jun 27, 2026

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