翻转二叉树的图解

public class 翻转二叉树 {
    public void midIteratorTree(TreeNode treeNode){
        if (null==treeNode){
            return;
        }
        System.out.print(treeNode.val+" ");
        midIteratorTree(treeNode.left );
        midIteratorTree(treeNode.right);
    }
    public TreeNode invertTree(TreeNode root){
        if (null==root){
            return root;
        }
        if (null==root.left&&null==root.right){
            return root;
        }
        invertTree(root.left);
        invertTree(root.right);
        TreeNode leftTree=root.left;
        root.left=root.right;
        root.right=leftTree;
        return root;
    }

    public static void main(String[] args) {
        TreeNode t1=new TreeNode(4);
        TreeNode t2=new TreeNode(2);
        TreeNode t3=new TreeNode(7);
        TreeNode t4=new TreeNode(1);
        TreeNode t5=new TreeNode(3);
        TreeNode t6=new TreeNode(6);
        TreeNode t7=new TreeNode(9);
        t1.left=t2;
        t1.right=t3;
        t2.left=t4;
        t2.right=t5;
        t3.left=t6;
        t3.right=t7;
        翻转二叉树 aa = new 翻转二叉树();
        System.out.println("---------");
        aa.midIteratorTree(t1);
        aa.invertTree(t1);
        System.out.println("-----------");
        aa.midIteratorTree(t1);

    }
}

class TreeNode {
    int val;
    TreeNode left;
    TreeNode right;

    TreeNode(int x) {
        val = x;
    }
}