Implement Trie (Prefix Tree)

Implement Trie (Prefix Tree)

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

Java代码：

class TrieNode {    private final int R = 26;    private final TrieNode[] children;    private String item;    public TrieNode() {        children = new TrieNode[R];        item = "";    }    public String getItem() {        return item;    }    public void setItem(String item) {        this.item = item;    }    public TrieNode[] getChildren() {        return children;    }    public TrieNode getChild(int i) {        if (i >= 26 || i < 0) throw new IllegalArgumentException();        return children[i];    }    public void setChild(int i, TrieNode node) {        children[i] = node;    }}public class Trie {    private TrieNode root;    public Trie() {        root = new TrieNode();    }    // Inserts a word into the trie.    public void insert(String word) {        TrieNode curr = root;        for (char c : word.toCharArray()) {            if (curr.getChild(c - 'a') == null) curr.setChild(c - 'a', new TrieNode());            curr = curr.getChild(c - 'a');        }        curr.setItem(word);    }    // Returns if the word is in the trie.    public boolean search(String word) {        TrieNode curr = root;        for (char c : word.toCharArray()) {            if (curr.getChild(c - 'a') == null) return false;            curr = curr.getChild(c - 'a');        }        return curr.getItem().equals(word);    }    // Returns if there is any word in the trie    // that starts with the given prefix.    public boolean startsWith(String prefix) {        TrieNode curr = root;        for (char c : prefix.toCharArray()) {            if (curr.getChild(c - 'a') == null) return false;            curr = curr.getChild(c - 'a');        }        return true;    }}// Your Trie object will be instantiated and called as such:// Trie trie = new Trie();// trie.insert("somestring");// trie.search("key");