LeetCode-101-对称二叉树

对称二叉树

解法一：递归

public class LeetCode_101 {
    public static boolean isSymmetric(TreeNode root) {
        if (root == null || (root.left == null && root.right == null)) {
            return true;
        }
        return isSymmetric(root.left, root.right);
    }

    public static boolean isSymmetric(TreeNode left, TreeNode right) {
        if (left == null && right == null) {
            return true;
        }
        if ((left == null && right != null) || (left != null && right == null)) {
            return false;
        }
        return left.val == right.val && isSymmetric(left.left, right.right) && isSymmetric(left.right, right.left);
    }

    public static void main(String[] args) {
        TreeNode root = new TreeNode(1);
        root.left = new TreeNode(2);
        root.right = new TreeNode(2);
        root.left.left = new TreeNode(3);
        root.right.right = new TreeNode(3);

        System.out.println(isSymmetric(root));
    }
}