题解 | #对称的二叉树#

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

    public TreeNode(int val) {
        this.val = val;

    }

}
*/
public class Solution {
    boolean isSymmetrical(TreeNode root) {
        if (root == null) {
            return true;
        }
        return isSymmetrical(root, root);
    }

    private boolean isSymmetrical(TreeNode left, TreeNode right) {
        if (left == null && right == null) {
            return true;
        }
        if (left == null || right == null) {
            return false;
        }
        return left.val == right.val && isSymmetrical(left.right, right.left) && isSymmetrical(left.left, right.right);
    }
}