230 二叉搜索树中第K小的元素class Solution: def kthSmallest(self, root: Optional[TreeNode], k: int) - int: ans0 def dfs(node: Optional[TreeNode]) - int: nonlocal k,ans if node is None or k0: return dfs(node.left) k-1 if k0: ansnode.val dfs(node.right) dfs(root) return ans199 二叉树的右视图class Solution: def rightSideView(self, root: Optional[TreeNode]) - List[int]: if root is None: return [] ans[] cur[root] while cur: ans.append(cur[-1].val) nxt[] for node in cur: if node.left:nxt.append(node.left) if node.right:nxt.append(node.right) curnxt return ans