题解 | #判断二叉树是否对称#

import java.util.*;

/*
 * public class TreeNode {
 *   int val = 0;
 *   TreeNode left = null;
 *   TreeNode right = null;
 * }
 */

public class Solution {
    /**
     * 
     * @param root TreeNode类 
     * @return bool布尔型
     */
   
    
    public boolean F2 (TreeNode root1,TreeNode root2){ //后序遍历
        if(root1==null && root2==null) return true;
        if(root1==null || root2==null) return false;
        if(root1.val!=root2.val) return false;
        return (F2(root1.left,root2.right)&&F2(root1.right,root2.left));
    }
    
    public boolean isSymmetric (TreeNode root) {
        // write code here 
       if(root==null) return true;
        return F2(root.left,root.right);
    }
}