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.
class TrieNode {
char val;
boolean isWord;
TrieNode[] children;
public TrieNode(char c) {
children = new TrieNode[26];
isWord = false;
val = c;
}
}
class Trie {
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++) {
char c = word.charAt(i);
if (cur.children[c - ‘a‘] == null) {
cur.children[c - ‘a‘] = new TrieNode(c);
}
cur = cur.children[c - ‘a‘];
}
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++) {
char c = word.charAt(i);
if (cur.children[c - ‘a‘] == null) {
return false;
}
cur = cur.children[c - ‘a‘];
}
if (cur.isWord) {
return true;
}
return false;
}
/** 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++) {
char c = prefix.charAt(i);
if (cur.children[c - ‘a‘] == null) {
return false;
}
cur = cur.children[c - ‘a‘];
}
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);
*/
LeetCode - Implement Trie (Prefix Tree)
原文：https://www.cnblogs.com/incrediblechangshuo/p/14401946.html