Implement Trie Prefix Tree

Author: TonyKim9401

implement-trie-prefix-tree/TonyKim9401.java

@@ -0,0 +1,56 @@
+class TrieNode {
+    TrieNode[] children;
+    boolean isEndOfWord;
+
+    public TrieNode() {
+        children = new TrieNode[26];
+        isEndOfWord = false;
+    }
+}
+
+class Trie {
+
+    private TrieNode root;
+
+    public Trie() {
+        root = new TrieNode();
+    }
+
+    // TC: O(n)
+    // SC: O(n * m)
+    // -> word length * new TrieNode spaces
+    public void insert(String word) {
+        TrieNode node = root;
+        for (char c : word.toCharArray()) {
+            int idx = c - 'a';
+            if (node.children[idx] == null) {
+                node.children[idx] = new TrieNode();
+            }
+            node = node.children[idx];
+        }
+        node.isEndOfWord = true;
+    }
+
+    // TC: O(n)
+    // SC: O(1)
+    public boolean search(String word) {
+        TrieNode node = searchPrefix(word);
+        return node != null && node.isEndOfWord;
+    }
+
+    // TC: O(n)
+    // SC: O(1)
+    private TrieNode searchPrefix(String word) {
+        TrieNode node = root;
+        for (char c : word.toCharArray()) {
+            int idx = c - 'a';
+            if (node.children[idx] == null) return null;
+            node = node.children[idx];
+        }
+        return node;
+    }
+
+    public boolean startsWith(String prefix) {
+        return searchPrefix(prefix) != null;
+    }
+}