题目:
Invert a binary tree.
4 / 2 7 / / 1 3 6 9
to
4 / 7 2 / / 9 6 3 1
Trivia:
This problem was inspired by this original tweet by Max Howell:
Google: 90% of our engineers use the software you wrote (Homebrew), but you can’t invert a binary tree on a whiteboard so fuck off.
链接: http://leetcode.com/problems/invert-binary-tree/
2/28/2017
1 public class Solution { 2 public TreeNode invertTree(TreeNode root) { 3 if (root == null) return root; 4 TreeNode tmp = new TreeNode(0); 5 if (root.left != null || root.right != null) { 6 tmp = root.right; 7 root.right = root.left; 8 root.left = tmp; 9 } 10 if (root.left != null) invertTree(root.left); 11 if (root.right != null) invertTree(root.right); 12 return root; 13 } 14 }
迭代的写法留给二刷?