Add serialize-and-deserialize-binary-tree solution in TS

Author: Jeehay28

serialize-and-deserialize-binary-tree/Jeehay28.ts

@@ -0,0 +1,52 @@
+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.
+ */
+
+// TC: O(n)
+// SC: O(n)
+function serialize(root: TreeNode | null): string {
+  if (!root) return "null";
+  return `${root.val},${serialize(root.left)},${serialize(root.right)}`;
+}
+
+/*
+ * Decodes your encoded data to tree.
+ */
+
+// TC: O(n)
+// SC: O(n)
+function deserialize(data: string): TreeNode | null {
+  const values = data.split(",");
+  let idx = 0;
+
+  const dfs = () => {
+    if (values[idx] === "null") {
+      idx++;
+      return null;
+    }
+
+    const node = new TreeNode(parseInt(values[idx]));
+    idx++;
+    node.left = dfs();
+    node.right = dfs();
+    return node;
+  };
+
+  return dfs();
+}
+
+/**
+ * Your functions will be called as such:
+ * deserialize(serialize(root));
+ */