Invert Binary Tree
Invert a binary tree. Example: Input: 4 / \ 2 7 / \ / \ 1 3 6 9 Output: 4 / \ 7 2 / \ / \ 9 6 3 1 /** * 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 null; } TreeNode right = invertTree(root.right); TreeNode left = invertTree(root.left); root.left = right; root.right = left; return root; } } Try it on Leetcode Here, we are going to solve it recursively. The inverse of an empty tree is the empty tree. The inverse of a tree with root r r r , and subtrees right and left , is a tree wit