字典树 02 在字典树中查询

查询单词word是否在Trie中

• 如果Trie中有word，那么word的每个字母，依次都能在Trie的每一行中找到（从Trie的第二行开始算起）；

// 查询单词word是否在Trie中
public boolean contains(String word){
    Node cur = root;
    for(int i = 0 ; i < word.length() ; i ++){
        char c = word.charAt(i);
        if(cur.next.get(c) == null)
            return false;
        cur = cur.next.get(c);
    }
    return cur.isWord;
}

对比BSTSet和Trie的速度

• Trie快；

public class Main {

    public static void main(String[] args) {
        System.out.println("Pride and Prejudice");

        ArrayList words = new ArrayList<>();
        if(FileOperation.readFile("pride-and-prejudice.txt", words)){

            long startTime = System.nanoTime();

            BSTSet set = new BSTSet<>();
            for(String word: words)
                set.add(word);
            for(String word: words)
                set.contains(word);

            long endTime = System.nanoTime();
            double time = (endTime - startTime) / 1000000000.0;
            System.out.println("Total different words: " + set.getSize());
            System.out.println("BSTSet: " + time + " s");

            // ---

            startTime = System.nanoTime();

            Trie trie = new Trie();
            for(String word: words)
                trie.add(word);

            for(String word: words)
                trie.contains(word);

            endTime = System.nanoTime();
            time = (endTime - startTime) / 1000000000.0;
            System.out.println("Total different words: " + trie.getSize());
            System.out.println("Trie: " + time + " s");
        }
    }
    
}

输出：

Pride and Prejudice
Total different words: 6530
BSTSet: 0.1964259 s
Total different words: 6530
Trie: 0.1082529 s