Knew it was backtracking pretty fast, which was a relief.
Use a depth-first search (DFS) with backtracking to explore all possible paths from each cell that matches the first character of the word. Mark cells as visited during the search and unmark them when backtracking to allow reuse in other paths. Return true if any path matches the entire word.
Pro tip: Before coding, clarify edge cases like empty grid, empty word, and whether the word can be longer than the total cells. Also, mention that you can optimize by checking if the word length exceeds the number of cells, and by pruning searches early if the remaining characters cannot be matched.
Restate the problem to ensure clarity: you need to find a path of adjacent cells (up, down, left, right) that spells the word, without reusing any cell. Discuss edge cases and constraints (e.g., grid dimensions, word length).
Select DFS with backtracking as the core approach. Explain why it's suitable: it explores all possible paths and backtracks when a path fails, ensuring no cell is reused within a single path.
Describe the DFS function: parameters (grid, word, current index, row, col, visited set). Base case: if index equals word length, return true. Check boundaries, character match, and visited status. Mark cell as visited, recurse in four directions, then unmark.
Loop through each cell in the grid; if the cell matches the first character of the word, start DFS from there. If any DFS returns true, return true immediately.
Discuss time complexity: O(m*n*4^L) where L is word length, and space complexity O(L) for recursion stack. Mention optimizations like early termination if word length > m*n, and using a visited matrix instead of a set for efficiency.
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