My first instinct was to reach for DFS and backtracking, which would've been completely wrong here.
Treat the grid as a graph where each cell is a potential starting point. For each cell that matches the first character of the word, explore all 8 directions, checking if the subsequent characters match along that straight line. If any direction yields a full match, return true; otherwise, continue until all cells are exhausted.
Pro tip: Clarify edge cases upfront, such as empty word, word longer than grid dimensions, and whether the word can be found in reverse. Also, discuss time and space complexity trade-offs, and mention that early termination when the remaining path is too short can optimize performance.
Confirm the definition of 'straight line' (8 directions), whether the word can be read forwards only or also backwards, and handle empty word or grid. Discuss constraints like grid size and word length.
List the 8 direction vectors (dx, dy). Write a helper function that, given a starting cell and a direction, checks if the word matches along that line without turning.
Loop through each cell in the grid. If the cell matches the first character of the word, try all 8 directions using the helper function. If any direction returns true, the word exists.
Before exploring a direction, check if the word can fit within the grid boundaries from the starting cell in that direction. Skip directions where the remaining length exceeds the available cells.
State time complexity O(N * M * 8 * L) where N, M are grid dimensions and L is word length, and space complexity O(1) excluding input. Mention that early termination and pruning can improve practical performance.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.