代码随想录第22天| 二叉树

LeetCode.235 二叉搜索树的最近公共祖先

后序遍历

if not root: return
left = self.lowestCommonAncestor(root.left, p, q)
right = self.lowestCommonAncestor(root.right, p, q)
if p.val < root.val and q.val < root.val: return left
if p.val > root.val and q.val > root.val: return right
return root

LeetCode.701 二叉搜索树中的插入操作

前序遍历

if not root: return TreeNode(val)
if val < root.val:
    if not root.left:
        root.left = TreeNode(val)
    else:
        self.insertIntoBST(root.left, val)
else:
    if not root.right:
        root.right = TreeNode(val)
    else:
        self.insertIntoBST(root.right, val)
return root

LeetCode.450 删除二叉搜索树中的节点

前序遍历

if not root: return
if root.val == key:
    if not root.left and not root.right: return
    if not root.left: return root.right
    if not root.right: return root.left
    node = root.right
    while node.left:
        node = node.left
    node.left = root.left
    return root.right
if key < root.val:
    root.left = self.deleteNode(root.left, key)
else:
    root.right = self.deleteNode(root.right, key)
return root