Word Search II (Trie & Backtracking)

To solve Word Search II efficiently, I would first construct a Trie from the provided list of words. This allows us to validate prefixes in constant time relative to the word length, which is crucial given Cisco's focus on scalable network protocols. If we simply ran a depth-first search for every word individually, the complexity would be prohibitive. Instead, by inserting all words into the Trie, we can traverse the 2D board once. For each cell, we initiate a backtracking search. As we move to adjacent cells, we check if the current path exists in the Trie. If it doesn't, we prune that branch immediately, saving significant computation. During the traversal, we mark the current cell as visited to avoid reusing it in the same path. When we reach a node in the Trie marked as a complete word, we add it to our results and optionally remove that node to prevent duplicates. Finally, we backtrack by unmarking the cell and returning to the previous state. This approach ensures we only explore valid prefixes, making the solution robust even with large input sizes typical in enterprise environments.