听力原文: Should a person own a car? This is an important question. In a large urban area, there are some good reasons for owning a car. Firstly, a car allows a person to move around freely. With a car there is no need to check a bus schedule or wait for a train. Secondly, a car is a comfortable way to travel, especially in the winter time. In bad weather, the driver stays warm and dry, while the poor bus or train rider might have to stand in the rain. Finally, a driver is usually safe in a car at night. The bus rider might need to walk down a dark street to get to a stop, or wait on a dark corner.
There are, on the other hand, many good reasons against owning a car. Firstly, it can be very expensive. The price of fuel continues to rise each year. In addition, it is expensive to maintain and repair a car. A simple repair can cost $ 50. In an urban area, it might also be expensive to park a car. Secondly, owning a car can cause worry and stress. It is exhausting to drive in heavy traffic. If you leave your car on the street, it might get stolen. That is something else to worry about.
(33)
A.Buses and trains are too crowded.
B.A person can move around freely.
C.It is easy to maintain cars.
D.A driver is usually safe in his car.
第1题
A.关键码个数最少的二叉搜索树
B.搜索时平均比较次数最少的二叉搜索树
C.所有结点的左子树都为空的二叉搜索树
D.所有结点的右子树都为空的二叉搜索树
第6题
设有一个关键码的输入序列(55,31,11,37,46,73,63,02,07):
(1)从空树开始构造平衡二叉搜索树,画出每加入一个新结点时二叉树的形态。若发生不平衡,指明需进行的平衡旋转的类型及平衡旋转的结果
(2)计算该平衡二叉搜索树在等概率下的搜索成功的平均搜索长度和搜索不成功的平均搜索长度。
第8题
A、二叉搜索树的查找时间效率是
B、二叉搜索树的前序遍历序列,是从小到大排列的
C、二叉搜索树的查找算法与二分法查找是等价的
D、同样一组数据,如果按照不同顺序插入到一棵初始状态为空的二叉搜索树当中,则产生的二叉搜索树形态有可能不同。
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