[Lintcode]Implement Trie 字典树

最新推荐文章于 2024-03-22 00:51:13 发布

青铁

最新推荐文章于 2024-03-22 00:51:13 发布

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分类专栏：算法文章标签： lintcode

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本文介绍了一种使用Trie树的数据结构来实现字符串的插入、搜索和前缀匹配的方法。通过具体的示例展示了如何构建Trie树节点，并实现了insert、search和startsWith等关键函数。

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Implement a trie with insert, search, and startsWith methods.

Example

insert("lintcode")
search("code") // return false
startsWith("lint") // return true
startsWith("linterror") // return false
insert("linterror")
search("lintcode) // return true
startsWith("linterror") // return true

分析：使用数组+布尔变量储存word信息。

/**
 * Your Trie object will be instantiated and called as such:
 * Trie trie = new Trie();
 * trie.insert("lintcode");
 * trie.search("lint"); will return false
 * trie.startsWith("lint"); will return true
 */
class TrieNode {
    TrieNode[] dict;
    boolean end;
    
    public TrieNode() {
        dict = new TrieNode[26];
        end = false;
    }
}

public class Trie {
    private TrieNode root;

    public Trie() {
        root = new TrieNode();
    }

    // Inserts a word into the trie.
    public void insert(String word) {
        TrieNode tmp = root;
        for(int i = 0; i < word.length(); i++) {
            char c = word.charAt(i);
            if(tmp.dict[c - 'a'] == null)
                tmp.dict[c - 'a'] = new TrieNode();
            tmp = tmp.dict[c - 'a'];
            if(i == word.length() - 1) tmp.end = true;
        }
    }

    // Returns if the word is in the trie.
    public boolean search(String word) {
        TrieNode tmp = root;
        for(int i = 0; i < word.length(); i++) {
            char c = word.charAt(i);
            if(tmp.dict[c - 'a'] == null) return false;
            tmp = tmp.dict[c - 'a'];
        }
        return tmp.end;
    }

    // Returns if there is any word in the trie
    // that starts with the given prefix.
    public boolean startsWith(String prefix) {
        TrieNode tmp = root;
        for(int i = 0; i < prefix.length(); i++) {
            char c = prefix.charAt(i);
            if(tmp.dict[c - 'a'] == null) return false;
            tmp = tmp.dict[c - 'a'];
        }
        return true;
    }
}