[Leetcode] 226. Invert Binary Tree JAVA

Topic:

Invert a binary tree.

     4   /     2     7/\   /1   3 6   9

To

     4   /     7     2/\   /9   6 3   1

test instructions and analysis: a binary tree is given, and the left and right sub-trees are exchanged on each node. For a node that needs to be exchanged, there are three cases: (1) There are left dial hand tree, no right subtree, (2) There is right subtree, no left subtree, (3) There are all sub-trees; in three cases, the left and right sub-trees are exchanged, and then the subtree can be recursive to get the result.

Code:

/*** Definition for a binary tree node. * public class TreeNode {* int val; * TreeNode left; * TreeNode rig Ht * TreeNode (int x) {val = x;} }*/ Public classSolution { PublicTreeNode inverttree (TreeNode root) {if(root==NULL)return NULL;        Exchange (root); returnRoot; }     Public voidExchange (TreeNode node) {if(node.left==NULL&&node.right==NULL)            return; Else{            if(node.left==NULL&&node.right!=NULL) {Node.left=Node.right; Node.right=NULL;                Exchange (Node.left); return; }Else if(node.right==NULL&&node.left!=NULL) {Node.right=Node.left; Node.left=NULL;            Exchange (Node.right); }Else{TreeNode temp=Node.left; Node.left=Node.right; Node.right=temp;                Exchange (Node.left);            Exchange (Node.right); }        }    }}

[Leetcode] 226. Invert Binary Tree JAVA