添加（0669.修剪二叉搜索树.md）：增加typescript版本

problems/0669.修剪二叉搜索树.md

@@ -405,6 +405,56 @@ var trimBST = function (root,low,high) {
  }
 ```
 
+## TypeScript
+
+> 递归法
+
+```typescript
+function trimBST(root: TreeNode | null, low: number, high: number): TreeNode | null {
+    if (root === null) return null;
+    if (root.val < low) {
+        return trimBST(root.right, low, high);
+    }
+    if (root.val > high) {
+        return trimBST(root.left, low, high);
+    }
+    root.left = trimBST(root.left, low, high);
+    root.right = trimBST(root.right, low, high);
+    return root;
+};
+```
+
+> 迭代法
+
+```typescript
+function trimBST(root: TreeNode | null, low: number, high: number): TreeNode | null {
+    while (root !== null && (root.val < low || root.val > high)) {
+        if (root.val < low) {
+            root = root.right;
+        } else if (root.val > high) {
+            root = root.left;
+        }
+    }
+    let curNode: TreeNode | null = root;
+    while (curNode !== null) {
+        while (curNode.left !== null && curNode.left.val < low) {
+            curNode.left = curNode.left.right;
+        }
+        curNode = curNode.left;
+    }
+    curNode = root;
+    while (curNode !== null) {
+        while (curNode.right !== null && curNode.right.val > high) {
+            curNode.right = curNode.right.left;
+        }
+        curNode = curNode.right;
+    }
+    return root;
+};
+```
+
+
+
 
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