# Add And Search Word Data Structure Design

## Add And Search Word   Data Structure Design

## 题目地址

<https://leetcode.com/problems/add-and-search-word-data-structure-design/>

## 题目描述

```
Design a data structure that supports the following two operations:

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:

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.
```

## 代码

Approach 1: Tire Tree

```java
class WordDictionary {
  public class TrieNode {
    public TrieNode[] children = new TrieNode[26];
    public String item = "";
  }

  private TrieNode root = new TrieNode();

  /** Initialize your data structure here. */
  public WordDictionary() {

  }

  /** Adds a word into the data structure. */
  public void addWord(String word) {
        TrieNode node = root;
    for (char c : word.toCharArray()) {
      if (node.children[c - 'a'] == null) {
        node.children[c - 'a'] = new TrieNode();
      }
      node = node.children[c - 'a'];
    }
    node.item = word;
  }

  /** 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 match(word.toCharArray(), 0, root);
  }

  private boolean math(chat[] chs, int k, TrieNode node) {
    if (k == chs.length)    return !node.item.equals("");
    if (chs[k] != '.') {
      return node.children[chs[k] - 'a'] != null &&
        match(chs, k + 1, node.children[chs[k] - 'a']);
    } else {
      for (int i = 0; i < node.children.length; i++) {
        if (node.children[i] != null) {
          if (match(chs, k + 1, node.children[i])) {
            return true;
          }
        }
      }
    }

    return false;
  }
}

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


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