trie tree

Author: genkimaru

src/main/java/com/leetcode/graph/Trie.java

@@ -0,0 +1,85 @@
+package com.leetcode.graph;
+
+class TrieNode {
+    // Links to child nodes
+    private TrieNode[] links;
+    // Marks the end of a word
+    private boolean isEnd;
+
+    public TrieNode() {
+        links = new TrieNode[26]; // Assuming only lowercase letters
+        isEnd = false;
+    }
+
+    public boolean containsKey(char ch) {
+        return links[ch - 'a'] != null;
+    }
+
+    public TrieNode get(char ch) {
+        return links[ch - 'a'];
+    }
+
+    public void put(char ch, TrieNode node) {
+        links[ch - 'a'] = node;
+    }
+
+    public void setEnd() {
+        isEnd = true;
+    }
+
+    public boolean isEnd() {
+        return isEnd;
+    }
+}
+
+public class Trie {
+    private TrieNode root;
+
+    public Trie() {
+        root = new TrieNode();
+    }
+
+    public void insert(String word) {
+        TrieNode node = root;
+        for (char ch : word.toCharArray()) {
+            if (!node.containsKey(ch)) {
+                node.put(ch, new TrieNode());
+            }
+            node = node.get(ch);
+        }
+        node.setEnd();
+    }
+
+    public boolean search(String word) {
+        TrieNode node = searchPrefix(word);
+        return node != null && node.isEnd();
+    }
+
+    public boolean startsWith(String prefix) {
+        TrieNode node = searchPrefix(prefix);
+        return node != null;
+    }
+
+    private TrieNode searchPrefix(String word) {
+        TrieNode node = root;
+        for (char ch : word.toCharArray()) {
+            if (node.containsKey(ch)) {
+                node = node.get(ch);
+            } else {
+                return null;
+            }
+        }
+        return node;
+    }
+
+    public static void main(String[] args) {
+        Trie trie = new Trie();
+        trie.insert("apple");
+        System.out.println(trie.search("apple")); // Output: true
+        System.out.println(trie.search("app"));   // Output: false
+        System.out.println(trie.startsWith("app")); // Output: true
+        trie.insert("app");
+        System.out.println(trie.search("app"));   // Output: true
+    }
+}
+