implement trie prefix tree solution

Author: hyunolike

implement-trie-prefix-tree/hyunolike.java

@@ -0,0 +1,54 @@
+class TrieNode {
+    TrieNode[] children = new TrieNode[26];
+    boolean isEnd;
+}
+
+class Trie {
+
+    private TrieNode root;
+
+    public Trie() {
+        root = new TrieNode();
+    }
+    
+    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.isEnd = true;
+    }
+    
+    public boolean search(String word) {
+        TrieNode node = root;
+        for(char c : word.toCharArray()) {
+            int idx = c - 'a'; 
+            if(node.children[idx] == null) return false;
+            node = node.children[idx];
+        }
+
+        return node.isEnd;
+    }
+    
+    public boolean startsWith(String prefix) {
+        TrieNode node = root;
+        for(char c : prefix.toCharArray()) {
+            int idx = c - 'a';
+            if(node.children[idx] == null) return false;
+            node = node.children[idx];
+        }
+        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);
+ */