关于leetcode:实现-Trie-前缀树

class Trie {
    class TrieNode {
        private boolean isEnd;
        private TrieNode[] links;

        TrieNode() {links = new TrieNode[26];
        }

        public boolean containsKey(char ch) {return links[ch-'a'] != null;
        }

        public TrieNode get(char ch) {return links[ch-'a'];
        }

        public void put(char ch, TrieNode node) {links[ch-'a'] = node;
        }

        public void setEnd() {isEnd = true;}

        public boolean isEnd() {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(char ch : word.toCharArray()) {if(!node.containsKey(ch)) {node.put(ch, new TrieNode());
            }
            node = node.get(ch);
        }
        node.setEnd();}
    
    /** Returns if the word is in the trie. */
    public boolean search(String word) {
        TrieNode node = root;
        for(char ch : word.toCharArray()) {if(!node.containsKey(ch)) {return false;}
            node = node.get(ch);
        }
        return node.isEnd();}
    
    /** Returns if there is any word in the trie that starts with the given prefix. */
    public boolean startsWith(String prefix) {
        TrieNode node = root;
        for(char ch : prefix.toCharArray()) {if(!node.containsKey(ch)) {return false;}
            node = node.get(ch);
        }
        return true;
    }
}

/**
 * Your Trie object will be instantiated and called as such:
 * Trie obj = new Trie();
 * obj.insert(word);
 * boolean param_2 = obj.search(word);
 * boolean param_3 = obj.startsWith(prefix);
 */