implement trie prefix tree solution

Author: JeonJe

implement-trie-prefix-tree/JeonJe.java

@@ -0,0 +1,47 @@
+// TC: O(L)
+// SC: O(N * L)
+class TrieNode {
+
+    public boolean isEnd;
+    public TrieNode[] children = new TrieNode[26];
+}
+
+class Trie {
+
+    private final TrieNode root;
+
+    public Trie() {
+        root = new TrieNode();
+    }
+
+    public void insert(String word) {
+        TrieNode node = root;
+        for (char c : word.toCharArray()) {
+            if (node.children[c - 'a'] == null) {
+                node.children[c - 'a'] = new TrieNode();
+            }
+            node = node.children[c - 'a'];
+        }
+        node.isEnd = true;
+    }
+
+    public boolean search(String word) {
+        TrieNode node = traverse(word);
+        return node != null && node.isEnd;
+    }
+
+    public boolean startsWith(String prefix) {
+        return traverse(prefix) != null;
+    }
+
+    private TrieNode traverse(String sequence) {
+        TrieNode node = root;
+        for (char c : sequence.toCharArray()) {
+            if (node.children[c - 'a'] == null) {
+                return null;
+            }
+            node = node.children[c - 'a'];
+        }
+        return node;
+    }
+}