Merge pull request neetcode-gh#53 from ArwaNayef/patch-3

Create 208-Implement-Trie(Prefix Tree)

Author: neetcode-gh

java/208-Implement-Trie(Prefix Tree)

@@ -0,0 +1,54 @@
+class Trie {
+    Node root;
+
+    public Trie() {
+        root = new Node('\0'); //dummy node
+    }
+
+    public void insert(String word) {
+        Node curr = root;
+        for (char x : word.toCharArray()) {
+            if (curr.children[x - 'a'] == null) {
+                curr.children[x - 'a'] = new Node(x);
+            }
+            curr = curr.children[x - 'a'];
+        }
+        curr.isWord = true;
+    }
+
+    public boolean search(String word) {
+        Node res = getLast(word);
+        return (res != null && res.isWord);
+    }
+
+    //helper method
+    public Node getLast(String word) {
+        Node curr = root;
+        for (char x : word.toCharArray()) {
+            if (curr.children[x - 'a'] == null) {
+                return null;
+            }
+
+            curr = curr.children[x - 'a'];
+        }
+        return curr;
+    }
+
+    public boolean startsWith(String prefix) {
+        Node res = getLast(prefix);
+        if (res == null) return false;
+        return true;
+    }
+
+    class Node {
+        private char value;
+        private boolean isWord;
+        private Node[] children;
+
+        public Node(char val) {
+            this.value = val;
+            this.isWord = false;
+            this.children = new Node[26];
+        }
+    }
+}