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226. Invert Binary Tree ​

题目 ​

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
Related Topics
  • 树
  • 深度优先搜索
  • 广度优先搜索
  • 二叉树

  • 👍 1970
  • 👎 0

    • 思路 ​

    递归解法

    解法 ​

    py
    # leetcode submit region begin(Prohibit modification and deletion)
# 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
# leetcode submit region end(Prohibit modification and deletion)

    复杂度分析 ​

    N 为二叉树节点， H为二叉树高度

    • 时间复杂度 O(N)
    • 空间复杂度 O(H)