添加（0700.二叉搜索树中的搜索.md）：增加typescript版本

problems/0700.二叉搜索树中的搜索.md

@@ -334,6 +334,36 @@ var searchBST = function (root, val) {
 };
 ```
 
+## TypeScript
+
+> 递归法
+
+```typescript
+function searchBST(root: TreeNode | null, val: number): TreeNode | null {
+    if (root === null || root.val === val) return root;
+    if (root.val < val) return searchBST(root.right, val);
+    if (root.val > val) return searchBST(root.left, val);
+    return null;
+};
+```
+
+> 迭代法
+
+```typescript
+function searchBST(root: TreeNode | null, val: number): TreeNode | null {
+    let resNode: TreeNode | null = root;
+    while (resNode !== null) {
+        if (resNode.val === val) return resNode;
+        if (resNode.val < val) {
+            resNode = resNode.right;
+        } else {
+            resNode = resNode.left;
+        }
+    }
+    return null;
+};
+```
+
 
 
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