Trie-based clean implementation in Java (beats 90.67% run times)


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    M
    public class WordDictionary {
        
        class TrieNode {
            boolean endHere;  // empty string, 1 node; string of length n, (n + 1) nodes.
            TrieNode[] branch;
            
            TrieNode () {
                endHere = false;
                branch = new TrieNode[26];
            }
        }
        
        TrieNode root = new TrieNode();
        
        // Adds a word into the data structure.
        public void addWord(String word) {
            addWord(word, 0, root);
        }
        
        private void addWord(String word, int p, TrieNode node) {
            if (p == word.length()) {
                node.endHere = true;
                return;
            }
            int index = word.charAt(p) - 'a';
            TrieNode succ = node.branch[index];
            if (succ == null) {
                succ = new TrieNode();
                node.branch[index] = succ;
            }
            addWord(word, p + 1, succ);
        }
    
        // Returns if the word is in the data structure. A word could
        // contain the dot character '.' to represent any one letter.
        public boolean search(String word) {
            return search(word, 0, root);
        }
        
        private boolean search(String word, int p, TrieNode node) {
            if (p == word.length()) { return node.endHere; }
            char c = word.charAt(p);
            if (c != '.') {
                if (node.branch[c - 'a'] == null) { return false; }
                return search(word, p + 1, node.branch[c - 'a']);
            } else {
                for (int i = 0; i < 26; ++i) {
                    if (node.branch[i] != null && search(word, p + 1, node.branch[i])) {
                        return true;
                    }
                }
            }
            return false;
        }
    }

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