add Implement Trie (Prefix Tree) solution

Author: HoonDongKang

implement-trie-prefix-tree/HoonDongKang.ts

@@ -0,0 +1,65 @@
+/**
+ * [Problem]: [208] Implement Trie (Prefix Tree)
+ * (https://leetcode.com/problems/implement-trie-prefix-tree/description/)
+ */
+
+class TrieNode {
+    children: { [key: string]: TrieNode };
+    isEnd: boolean;
+
+    constructor() {
+        this.children = {};
+        this.isEnd = false;
+    }
+}
+
+class Trie {
+    constructor(private root = new TrieNode()) {}
+
+    //시간복잡도: O(n)
+    //공간복잡도: O(n)
+    insert(word: string): void {
+        let node = this.root;
+        for (let char of word) {
+            if (!node.children[char]) {
+                node.children[char] = new TrieNode();
+            }
+
+            node = node.children[char];
+        }
+
+        node.isEnd = true;
+    }
+
+    //시간복잡도: O(n)
+    //공간복잡도: O(n)
+    search(word: string): boolean {
+        let node = this.root;
+        for (let char of word) {
+            if (!node.children[char]) return false;
+            node = node.children[char];
+        }
+
+        return node.isEnd;
+    }
+
+    //시간복잡도: O(n)
+    //공간복잡도: O(n)
+    startsWith(prefix: string): boolean {
+        let node = this.root;
+        for (let char of prefix) {
+            if (!node.children[char]) return false;
+            node = node.children[char];
+        }
+
+        return true;
+    }
+}
+
+/**
+ * Your Trie object will be instantiated and called as such:
+ * var obj = new Trie()
+ * obj.insert(word)
+ * var param_2 = obj.search(word)
+ * var param_3 = obj.startsWith(prefix)
+ */