59.对称的二叉树

package com.yuan.demo6;

/**
 * @author QLBF
 * @version 1.0
 * @date 2021/6/10 9:29
 */
class TreeNode{
    String val;
    TreeNode left;
    TreeNode right;

    public TreeNode(String val) {
        this.val = val;
    }
}
public class test6 {

    public static boolean isSymmetrical(TreeNode root){
        if (root==null){
            return true;
        }

        return isSymmetrical(root.left,root.right);
    }

    private static boolean isSymmetrical(TreeNode root1, TreeNode root2) {
        if (root1 ==null && root2==null){return true;}
        if (root1==null || root2==null){
            return false;
        }

        if (root1.val != root2.val){
            return false;
        }

        return isSymmetrical(root1.left,root2.right)&& isSymmetrical(root1.right,root2.left);
    }

    public static void main(String[] args) {
        TreeNode rootnode=new TreeNode("A");
        TreeNode t2=new TreeNode("B");
        TreeNode t3=new TreeNode("B");
        TreeNode t4=new TreeNode("C");
        TreeNode t5=new TreeNode("D");
        TreeNode t6=new TreeNode("D");
        TreeNode t7=new TreeNode("C");
        rootnode.left=t2;
        rootnode.right=t3;
        t2.left=t4;
        t2.right=t5;
        t3.left=t6;
        t3.right=t7;

        boolean symmetrical = isSymmetrical(rootnode);
        System.out.println(symmetrical);
    }
}

参考：https://blog.youkuaiyun.com/weixin_41163113/article/details/88081868