208. Implement Trie (Prefix Tree)
class Trie {
class TrieNode {
private boolean isWord;
private TrieNode[] children;
public TrieNode() {
isWord = false;
children = new TrieNode[26];
}
}
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 cur = root;
for (int i = 0; i < word.length(); i++) {
int index = word.charAt(i) - 'a';
if (cur.children[index] == null) {
cur.children[index] = new TrieNode();
}
cur = cur.children[index];
}
cur.isWord = true;
}
/** Returns if the word is in the trie. */
public boolean search(String word) {
TrieNode cur = root;
for (int i = 0; i < word.length(); i++) {
int index = word.charAt(i) - 'a';
if (cur.children[index] == null) {
return false;
}
cur = cur.children[index];
}
return cur.isWord;
}
/** Returns if there is any word in the trie that starts with the given prefix. */
public boolean startsWith(String prefix) {
TrieNode cur = root;
for (int i = 0; i < prefix.length(); i++) {
int index = prefix.charAt(i) - 'a';
if (cur.children[index] == null) {
return false;
}
cur = cur.children[index];
}
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);
*/