Leetcode 208. Implement Trie (Prefix Tree)

最新推荐文章于 2024-01-22 12:36:44 发布

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本文介绍了一种Trie树（字典树）的数据结构实现方法，并提供了详细的Java代码示例。通过该实现，可以高效地完成字符串的插入、搜索及前缀匹配等功能。

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public class Trie {
    
    public static class TrieNode {
        private final int N = 26;
        
        private TrieNode[] links;
        
        private boolean isEnd = false;
        
        public TrieNode() {
            links = new TrieNode[N];
        }
        
        public boolean containsKey(char ch) {
            return links[ch-'a'] != null;            
        }
        
        public void insertKey(char ch, TrieNode node) {
            links[ch-'a'] = node;
        }
        
        public TrieNode getNode(char ch) {
            return links[ch-'a'];
        }
        
        public void setEnd() {
            isEnd = true;
        }
        
        public boolean getEnd() {
            return isEnd;
        }
        
    }

    private TrieNode root;

    /** Initialize your data structure here. */
    public Trie() {
         root = new TrieNode();
    }
    
    /** Inserts a word into the trie. */
    public void insert(String word) {
        TrieNode node = root;
        for (int i=0; i<word.length(); i++) {
            char curr = word.charAt(i);
            if (!node.containsKey(curr)) {
                node.insertKey(curr, new TrieNode());
            }
            node = node.getNode(curr);
        }
        node.setEnd();
    }
    
    /** Returns null or a TrieNode which the last char in the word points **/
    public TrieNode searchPrefix(String word) {
        TrieNode node = root;
        for (int i=0; i<word.length(); i++) {
            char curr = word.charAt(i);
            if (!node.containsKey(curr)) {
                node = null;
                break;
            } 
            node = node.getNode(curr);
        }
        return node;
    }
    
    /** Returns if the word is in the trie. */
    public boolean search(String word) {
        TrieNode node = searchPrefix(word);
        return node!=null && node.getEnd();
    }
    
    /** Returns if there is any word in the trie that starts with the given prefix. */
    public boolean startsWith(String prefix) {
        TrieNode node = searchPrefix(prefix);
        return node != null;
    }
}