前序遍历(DLR) ①访问根结点; ②以前序遍历方式遍历根结点的左子树; ③以前序遍历方式遍历根结点的右子树。
A campus emergency ______ occur at any time of the day or night, weekend, or holiday, with little or no warning.
免费的网站请分享给朋友吧