226. Invert Binary Tree

📋 Đề Bài

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

🧠 Thuật Toán & Kỹ Thuật

Tree Traversal (Duyệt cây)

⏱️ Thời gian O(n)

💾 Không gian O(1)

💻 Lời Giải

Python 0226-invert-binary-tree.py

# 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 None
        
        dq = deque([root])
        
        while dq:
            node = dq.popleft()
            
            if node.left:
                dq.append(node.left)
                
            if node.right:
                dq.append(node.right)
            
            node.left, node.right = node.right, node.left
        
        return root