211. Design Add and Search Words Data Structure[Medium]

211. Design Add and Search Words Data Structure

Design a data structure that supports adding new words and finding if a string matches any previously added string.

Implement the WordDictionary class:

• WordDictionary() Initializes the object.
• void addWord(word) Adds word to the data structure, it can be matched later.
• bool search(word) Returns true if there is any string in the data structure that matches word or falseotherwise. word may contain dots '.' where dots can be matched with any letter.

Constraints:

• 1 <= word.length <= 25
• word in addWord consists of lowercase English letters.
• word in search consist of '.' or lowercase English letters.
• There will be at most 3 dots in word for search queries.
• At most 10^4 calls will be made to addWord and search.

Example

Input
["WordDictionary","addWord","addWord","addWord","search","search","search","search"]
[[],["bad"],["dad"],["mad"],["pad"],["bad"],[".ad"],["b.."]]
Output
[null,null,null,null,false,true,true,true]

Explanation
WordDictionary wordDictionary = new WordDictionary();
wordDictionary.addWord("bad");
wordDictionary.addWord("dad");
wordDictionary.addWord("mad");
wordDictionary.search("pad"); // return False
wordDictionary.search("bad"); // return True
wordDictionary.search(".ad"); // return True
wordDictionary.search("b.."); // return True

思路

题解

   class TrieNode {
        HashMap<Character, TrieNode> node = new HashMap<>();
        boolean isEnd;
    }

    TrieNode root = new TrieNode();

    public void addWord(String word) {
        char[] data = word.toCharArray();
        TrieNode cur = root;
        for (char val : data) {
            if (!cur.node.containsKey(val))
                cur.node.put(val, new TrieNode());
            cur = cur.node.get(val);
        }
        cur.isEnd = true;
    }

    public boolean search(String word) {
        char[] data = word.toCharArray();
        TrieNode cur = root;
        return dfsSearch(word, cur);
    }

    public boolean dfsSearch(String word, TrieNode cur) {
        char[] data = word.toCharArray();
        for (int i = 0; i < data.length; i++) {
            if (data[i] == '.') {
                for (TrieNode value : cur.node.values()) {
                    if (dfsSearch(word.substring(i + 1), value))
                        return true;
                }
            }
            if (!cur.node.containsKey(data[i]))
                return false;
            cur = cur.node.get(data[i]);
        }
        return cur.isEnd;
    }