牛客（17）树的子结构

    //    题目描述
//    输入两棵二叉树A，B，判断B是不是A的子结构。（ps：我们约定空树不是任意一个树的子结构）
    public static class TreeNode {
        int val = 0;
        TreeNode left = null;
        TreeNode right = null;

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

        }
    }

    public static boolean HasSubtree(TreeNode root1, TreeNode root2) {
        if (root1 == null || root2 == null) {
            return false;
        }
        boolean result = false;


        if (root1.val == root1.val) {
            result = equalsTree(root1, root2);
        }
        if (!result) {
            result = HasSubtree(root1.left, root2);
        }
        if (!result) {
            result = HasSubtree(root1.right, root2);
        }
        return result;
    }

    public static boolean equalsTree(TreeNode root1, TreeNode root2) {
        if (root2 == null) {
            return true;
        }
        if (root1 == null) {
            return false;
        }
        if (root1.val == root2.val) {
            return equalsTree(root1.right, root2.right) && equalsTree(root1.left, root2.left);
        }
        return false;
    }