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.
Solution:
class Trie {
Trie[] children = new Trie[26];
boolean isLeaf = false;
/** Initialize your data structure here. */
public Trie() {
}
/** Inserts a word into the trie. */
public void insert(String word) {
Trie node = this;
for (int i = 0; i < word.length(); i++) {
char c = word.charAt(i);
if (node.children[c - 'a'] == null) {
node.children[c - 'a'] = new Trie();;
}
node = node.children[c - 'a'];
}
node.isLeaf = true;
}
/** Returns if the word is in the trie. */
public boolean search(String word) {
Trie node = this;
for (int i = 0; i < word.length(); i++) {
char c = word.charAt(i);
node = node.children[c - 'a'];
if (node == null) {
return false;
}
}
return node.isLeaf;
}
/** Returns if there is any word in the trie that starts with the given prefix. */
public boolean startsWith(String prefix) {
Trie node = this;
for (int i = 0; i < prefix.length(); i++) {
char c = prefix.charAt(i);
node = node.children[c - 'a'];
if (node == null) {
return false;
}
}
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);
*/