How to flip binary Tree in LeetCode
This article mainly introduces how to flip the binary tree in LeetCode, which is very detailed and has a certain reference value. Interested friends must read it!
Topic description:
Flip a binary tree.
Example:
Enter:
Output:
Analysis of ideas:
Through observation, we find that as long as the left and right child nodes of each node on the binary tree are exchanged, the final result is the binary tree completely flipped.
This topic is relatively simple, the key idea is that we find that flipping the whole tree is to swap the left and right child nodes of each node, so we put the code of swapping the left and right child nodes in the preorder traversal position.
It is worth mentioning that it is also possible to exchange the code of the left and right child nodes in the post-order traversal position, but not in the middle-order traversal position.
Java implementation / * *
* Definition for a binary tree node.
* public class TreeNode {
* int val
* TreeNode left
* TreeNode right
* TreeNode () {}
* TreeNode (int val) {this.val = val;}
* TreeNode (int val, TreeNode left, TreeNode right) {
* this.val = val
* this.left = left
* this.right = right
*}
*}
, /
Class Solution {
Public TreeNode invertTree (TreeNode root) {
If (root==null) {
Return root
}
TreeNode tmp=root.left
Root.left=root.right
Root.right=tmp
InvertTree (root.left)
InvertTree (root.right)
Return root
}
}
Python implements class Solution:
Def invertTree (self, root: TreeNode)-> TreeNode:
If not root:
Return root
Left = self.invertTree (root.left)
Right = self.invertTree (root.right)
Root.left, root.right = right, left
Return root
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