每日一题：判断一颗二叉树是否是镜面树

题目描述：判断一颗二叉树是否是镜面树，说白了就是这棵树是否是按照中轴左右对称的。

/**
 * 测试链接：https://leetcode.com/problems/symmetric-tree
 * 题目描述：判断一颗二叉树是否是镜面树
 */
public class Code02_SymmetricTree {
    public static class TreeNode {
        public int val;
        public TreeNode left;
        public TreeNode right;
    }

    public static boolean isSymmetric(TreeNode root) {
        return isMirror(root, root);
    }

    /**
     * h1和h2是同一棵树，只是一个往左走，一个往右走
     * @param h1
     * @param h2
     * @return
     */
    public static boolean isMirror(TreeNode h1,TreeNode h2){
        if (h1 == null ^ h2 == null){
            return false;
        }
        if (h1 == null && h2 == null){
            return true;
        }
        return h1.val == h2.val && isMirror(h1.left,h2.right) && isMirror(h1.right,h2.left);
    }
}