[Leetcode/파이썬] 226. Invert Binary Tree

Invert Binary Tree

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Given the root of a binary tree, invert the tree, and return its root.

 

Example 1:

Input: root = [4,2,7,1,3,6,9]
Output: [4,7,2,9,6,3,1]

Example 2:

Input: root = [2,1,3]
Output: [2,3,1]

Example 3:

Input: root = []
Output: []

 

Constraints:

• The number of nodes in the tree is in the range [0, 100].
• -100 <= Node.val <= 100

 

# 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 invertTree(self, root: Optional[TreeNode]) -> Optional[TreeNode]:
        if root is None :
            return None

        tmp = root.left
        root.left = root.right
        root.right = tmp

        self.invertTree(root.left)
        self.invertTree(root.right)

        return root

# 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 invertTree(self, root: Optional[TreeNode]) -> Optional[TreeNode]:
        if not root :
            return
        root.left, root.right = self.invertTree(root.right), self.invertTree(root.left)
        return root

이 문제는 생소해서 해결하지 못했다. 답안 코드를 봐도 처음에 이해하지 못해서 이거저거 찾아보다가 첫 번째 코드가 이해하기 쉬워서 들고왔다. 이런 문제는 왜이렇게 어려울까.