450. Delete Node in a BST (Medium) - TengnanYao/daily_leetcode GitHub Wiki

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def deleteNode(self, root: Optional[TreeNode], key: int) -> Optional[TreeNode]:
        dummy = TreeNode(val = inf, left = root)
        q = [dummy]
        while q:
            node = q.pop()
            if node.left:
                x = node.left
                if x.val == key:
                    if not x.left and not x.right:
                        node.left = None
                    elif x.left:
                        node.left = x.left
                        y = x.left
                        while y.right:
                            y = y.right
                        y.right = x.right
                    else:
                        node.left = x.right
                    return dummy.left
                q.append(node.left)
            if node.right:
                x = node.right
                if x.val == key:
                    if not x.left and not x.right:
                        node.right = None
                    elif x.left:
                        node.right = x.left
                        y = x.left
                        while y.right:
                            y = y.right
                        y.right = x.right
                    else:
                        node.right = x.right
                    return dummy.left
                q.append(node.right)
        return dummy.left