Word Dictionary with Wildcards (Trie)

To solve the Word Dictionary with Wildcards problem, I would implement a modified Trie structure. First, we define a Node class containing a map or array of 26 characters and a boolean flag indicating the end of a valid word. The insert operation remains standard, traversing down the tree and creating nodes only when necessary, ensuring O(M) time complexity where M is the word length. The critical part is the search method. For exact matches, we traverse linearly. However, when we encounter a '.', we must branch out. Instead of checking a specific index, I would write a recursive helper function. This function takes the current node and the remaining query string. If the current character is a letter, we move to that specific child if it exists. If it is a '.', we loop through every non-null child node and recursively call the search function for the rest of the string. This approach effectively performs a Depth-First Search. We return true immediately if any recursive branch finds a complete match. If all branches fail, we backtrack. While the worst-case complexity increases due to branching, this solution efficiently handles the wildcard requirement. In an IBM context, where reliability is key, I would also add boundary checks to ensure we don't access null pointers during the traversal, making the implementation robust for large-scale dictionary services.