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/**

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

*

* Example:

*

* Trie trie = new Trie();

*

* trie.insert("apple");

* trie.search("apple"); // returns true

* trie.search("app"); // returns false

* trie.startsWith("app"); // returns true

* trie.insert("app");

* trie.search("app"); // returns true

*

* Note:

* You may assume that all inputs are consist of lowercase letters a-z.

* All inputs are guaranteed to be non-empty strings.

*/

public class ImplementTriePrefixTree208 {

class Trie {

private Trie[] children = new Trie[26];

private boolean isWord = false;

/** Initialize your data structure here. */

public Trie() {

}

/** Inserts a word into the trie. */

public void insert(String word) {

insert(word.toCharArray(), 0);

}

private void insert(char[] chars, int i) {

if (i == chars.length) {

this.isWord = true;

return;

}

if (this.children[chars[i]-'a'] == null) {

this.children[chars[i]-'a'] = new Trie();

}

this.children[chars[i]-'a'].insert(chars, i+1);

}

/** Returns if the word is in the trie. */

public boolean search(String word) {

return search(word.toCharArray(), 0);

}

private boolean search(char[] chars, int i) {

if (i == chars.length) return this.isWord;

if (this.children[chars[i]-'a'] == null) return false;

return this.children[chars[i]-'a'].search(chars, i+1);

}

/** Returns if there is any word in the trie that starts with the given prefix. */

public boolean startsWith(String prefix) {

return startsWith(prefix.toCharArray(), 0);

}

private boolean startsWith(char[] chars, int i) {

if (i == chars.length) return true;

if (this.children[chars[i]-'a'] == null) return false;

return this.children[chars[i]-'a'].startsWith(chars, i+1);

}

}

/**

* https://leetcode.com/problems/implement-trie-prefix-tree/solution/

*/

class Trie2 {

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 c = word.charAt(i);

if (!node.containsKey(c)) {

node.put(c, new TrieNode());

}

node = node.get(c);

}

node.setLeaf();

}

/** Returns if the word is in the trie. */

public boolean search(String word) {

TrieNode node = root;

for (int i = 0; i < word.length(); i++) {

char c = word.charAt(i);

if (!node.containsKey(c)) {

return false;

}

node = node.get(c);

}

return node.isLeaf();

}

/** Returns if there is any word in the trie that starts with the given prefix. */

public boolean startsWith(String prefix) {

TrieNode node = root;

for (int i = 0; i < prefix.length(); i++) {

char c = prefix.charAt(i);

if (!node.containsKey(c)) {

return false;

}

node = node.get(c);

}

return true;

}

}

class TrieNode {

// R links to node children

private TrieNode[] links;

private final int R = 26;

private boolean isLeaf;

public TrieNode() {

links = new TrieNode[R];

}

public boolean containsKey(char c) {

return links[c -'a'] != null;

}

public TrieNode get(char c) {

return links[c -'a'];

}

public void put(char c, TrieNode node) {

links[c -'a'] = node;

}

public void setLeaf() {

isLeaf = true;

}

public boolean isLeaf() {

return isLeaf;

}

}

/**

* 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);

*/

}