斯坦福大学开放课程——编程方法 作业1-1

Problem 1
Your first task is to solve a simple story-problem  in Karel’s world.  Suppose that Karel has settled into its house, which is the square area in the center of the following diagram:

Karel starts off in the northwest corner of its house as shown in the diagram. The problem you need to get Karel to solve is to collect the newspaper—represented (as all objects in Karel’s world are) by a beeper—from outside the doorway and then to return to its initial position.
 
This exercise is extremely simple and exists just to get you started.  You can assume that every part of the world looks just as it does in the diagram.  The house is exactly this size, the door is always in the position shown, and the beeper is just outside the door.  Thus, all you have to do is write the sequence of commands necessary to have Karel
 
1. Move to the newspaper,
2. Pick it up, and
3. Return to its starting point.
 
Even though the program is only a few lines, it is still worth getting at least a little practice in decomposition.  In your solution, include a private method for each of the steps shown in the outline.

 

源代码：

/* * File: CollectNewspaperKarel.java * -------------------------------- * At present, the CollectNewspaperKarel subclass does nothing. * Your job in the assignment is to add the necessary code to * instruct Karel to walk to the door of its house, pick up the * newspaper (represented by a beeper, of course), and then return * to its initial position in the upper left corner of the house. */import stanford.karel.*;public class CollectNewspaperKarel extends SuperKarel {public void run(){/* 取报纸 */goToCollect();/* 返回初始位置 */goBack();}/*取报纸*/private void goToCollect(){move2wall();move2door();pickNewpaper();}/*移动到墙壁之前*/private void move2wall(){while(frontIsClear()){move();}}/*沿着墙走到门前*/private void move2door(){turnRight();while(leftIsBlocked()){move();}turnLeft();}/*捡起新报纸*/private void pickNewpaper(){move();pickBeeper();}/*返回初始位置*/private void goBack(){turnAround();while(frontIsClear()){move();}turnRight();move();turnRight();}}

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演示视频地址： http://v.youku.com/v_show/id_XMjI5NDg1Nzc2.html

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