add Serialize and Deserialize Binary Tree solution

Author: HoonDongKang

serialize-and-deserialize-binary-tree/HoonDongKang.ts

@@ -0,0 +1,54 @@
+/**
+ * [Problem]: [297] Serialize and Deserialize Binary Tree
+ * (\https://leetcode.com/problems/serialize-and-deserialize-binary-tree/description/)
+ */
+
+class TreeNode {
+    val: number;
+    left: TreeNode | null;
+    right: TreeNode | null;
+    constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
+        this.val = val === undefined ? 0 : val;
+        this.left = left === undefined ? null : left;
+        this.right = right === undefined ? null : right;
+    }
+}
+
+/*
+ * Encodes a tree to a single string.
+ */
+//시간복잡도 O(N)
+//공간복잡도 O(N)
+function serialize(root: TreeNode | null): string {
+    if (!root) return "NULL";
+
+    const left = serialize(root.left);
+    const right = serialize(root.right);
+
+    return `${root.val},${left},${right}`;
+}
+
+/*
+ * Decodes your encoded data to tree.
+ */
+//시간복잡도 O(N)
+//공간복잡도 O(N)
+function deserialize(data: string): TreeNode | null {
+    const values = data.split(",");
+    let index = 0;
+
+    function dfs(): TreeNode | null {
+        if (values[index] === "NULL") {
+            index++;
+            return null;
+        }
+        const node = new TreeNode(+values[index++]);
+
+        node.left = dfs();
+        node.right = dfs();
+
+        return node;
+    }
+
+    return dfs();
+}