stanford编程方法学karel作业一problem3

/*
* File: MidpointFindingKarel.java
* -------------------------------
* When you finish writing it, the MidpointFindingKarel class should
* leave a beeper on the corner closest to the center of 1st Street
* (or either of the two central corners if 1st Street has an even
* number of corners). Karel can put down additional beepers as it
* looks for the midpoint, but must pick them up again before it
* stops. The world may be of any size, but you are allowed to
* assume that it is at least as tall as it is wide.
*
* author:zhendongYi
* time:2016/06/27
* 我采用的方法是首先铺满一层beeper，然后从两端各自清除一个beeper，循环清除
* 直到最后beeper数量小于等于2结束
* **********************************
* 由于看错了题目要求，以为偶数的行需要中间两个格子都放上beeper，结果只需要
* 随便放一个beeper即可，懒得改了，再加一个判断就可
*/

import stanford.karel.*;

public class MidpointFindingKarel extends SuperKarel {

    public void run(){
        putLineBlocks();                //将一行填满方块,并转向
        removeBlocksStepByStep();       //循环从左边和右边各移动一个方块
    }

    //填满一行方块,并转向
    private void putLineBlocks() {
        while(frontIsClear()){
            putBeeper();
            move();
        }
        putBeeper();
        turnAround();
        
    }

    // 如果beeper数量大于2，则循环清除左右两边的方块，否则什么也不做
    private void removeBlocksStepByStep() {
        while(blockNumber()>2){ 
            moveToBlockEnd();
            removeBlock();
            moveToBlockEnd();
            removeBlock();      
        }
    }
    
    //移除最边上的beeper,并前进一小格，走到beeper的地方
    private void removeBlock() {
        pickBeeper();
        move();
    }

    /*
     * 条件：karel位于有block的一端
     * 结果：karel跑到有block的另一端，i为block数量，并转向两次以避免奇数次对循环造成影响
     */
    private int blockNumber() {
        // 计算所有的block的数量
        int i=0;
        while(beepersPresent()){
            i++;
            if(frontIsClear()){
                move();
            }else{
                break;
            }
        }
        turnAround();
        
        
        //再转回来
        while(beepersPresent()){
            if(frontIsClear()){
                move();
            }else{
                break;
            }
        }
        turnAround();
        return i;
        
    }

    /*
     * 将karel移到存在beeper所有的位置的最边上的一点
     */
    private void moveToBlockEnd() {
        while(frontIsClear()&&beepersPresent()){
            move();
        }
        if(noBeepersPresent()){
            turnAround();
            move();
        }else{
            turnAround();
        }
    }
    
}