leetcode 211 Add and Search Word - Data structure design
z
 2019-04-07 17:33:40  

Design a data structure that supports the following two operations:

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void addWord(word)
bool search(word)

search(word) can search a literal word or a regular expression string containing only letters a-z or .. A . means it can represent any one letter.

Example:

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addWord("bad")
addWord("dad")
addWord("mad")
search("pad") -> false
search("bad") -> true
search(".ad") -> true
search("b..") -> true

Note:
You may assume that all words are consist of lowercase letters a-z.

  • 可以使用trie数来处理
  • 主要是处理.的问题
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class WordDictionary {
    class Node {
        Node[] next;
        boolean isWord;
        
        public Node() {
            next = new Node[26];
        };
    }
    
    Node root = new Node();
    
    /** Initialize your data structure here. */
    public WordDictionary() {
    }
    
    /** Adds a word into the data structure. */
    public void addWord(String word) {
        Node p = root;
            for (char c: word.toCharArray()) {
                if (p.next[c-'a'] == null) {
                    p.next[c-'a'] = new Node();
                }
                p = p.next[c-'a'];
            }
            p.isWord = true;
    }
    
    /** 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 find(word, root);
    }
    
    public boolean find(String word, Node p) {
        for (int i=0; i<word.length(); i++) {
            char c = word.charAt(i);
            if (c>='a' && c<='z') {
                if (p.next[c-'a'] == null) {
                    return false;
                }
                p = p.next[c-'a'];
            }
            else {
                boolean find = false;
                for (Node n: p.next) {
                    if (n != null) {
                        find = (find || find(word.substring(i+1), n));
                    }
                }
                return find;
            }  
        }
        return p.isWord;
    }
}

/**
 * Your WordDictionary object will be instantiated and called as such:
 * WordDictionary obj = new WordDictionary();
 * obj.addWord(word);
 * boolean param_2 = obj.search(word);
 */