stanford编程方法学karel作业一problem4

/*
* File: CheckerboardKarel.java
* ----------------------------
* When you finish writing it, the CheckerboardKarel class should draw
* a checkerboard using beepers, as described in Assignment 1. You
* should make sure that your program works for all of the sample
* worlds supplied in the starter folder.
* 算法：以一条龙的方式前进，每走两格，放置一个beeper
* 关键：转向的判断
*
* 转向：无论何时遇到障碍，将karel转至朝北方向，然后前进，再转向没有障碍的一侧
* 待改进：最后运行时无法正常停止，直到被阻挡
*/

    import stanford.karel.*;
    
    public class CheckerboardKarel extends SuperKarel {
        public void run(){
            putBeeper();                    //首先放置一个beeper
            while(LoopCondition()){         //满足循环条件的话就继续
                moveOn();                   //前进一格（直走或者转向都算前进）
                moveOn();                   //继续前进一格
                putBeeper();                //放置一个beeper
            }
        }
    
    
        /*
         * 前进一格，直走或者转向并move
         * 如果前方是空的话，move，
         * 否则，向上拐，并转向
         */
        private void moveOn() {
            if(frontIsClear()){
                move();
            }else{
                upAndTurnAround();
            }
            
        }
    
        /*
         * 向上拐并转向
         * 首先将方向朝向北，然后向上转并转向
         */
        private void upAndTurnAround() {
            // TODO Auto-generated method stub
            faceToNorth();
            upAndTurn();
        }
    
        /*
         * 前进，并根据左右情况转向
         */
        private void upAndTurn() {
            move();
            if(leftIsClear()){
                turnLeft();
            }else{
                turnRight();
            }
        }
    
        /*
         * 转向，直到面朝北
         */
        private void faceToNorth() {
            // TODO Auto-generated method stub
            while(notFacingNorth()){
                turnLeft();         
            }
        }
    
        /*
         * 循环条件函数
         * 根据前左右的情况判断是否继续循环
         */
        private boolean LoopCondition() {
            // TODO Auto-generated method stub
            return (frontIsClear()||leftIsClear())&&(frontIsClear()||rightIsClear());
        }
    
    }