serialize and deserialize binary tree solution

Author: hyer0705

serialize-and-deserialize-binary-tree/hyer0705.ts

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+/**
+ * Definition for a binary tree node.
+ * 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.
+ */
+function serialize(root: TreeNode | null): string {
+  if (!root) return "null";
+
+  let result = "" + root.val;
+
+  result += "," + serialize(root.left);
+  result += "," + serialize(root.right);
+
+  return result;
+}
+
+/*
+ * Decodes your encoded data to tree.
+ */
+function deserialize(data: string): TreeNode | null {
+  const values = data.split(",");
+  let index = 0;
+
+  const buildTree = () => {
+    const val = values[index];
+    index++;
+
+    if (val === "null") return null;
+
+    const node = new TreeNode(Number(val));
+    node.left = buildTree();
+    node.right = buildTree();
+    return node;
+  };
+
+  return buildTree();
+}
+
+/**
+ * Your functions will be called as such:
+ * deserialize(serialize(root));
+ */