CheckerboardKarel

/*
 * 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.
 */

import stanford.karel.*;

public class CheckerboardKarel extends SuperKarel {
        public void run () {
                makeCheckerBoard () ;
        }

        private void makeCheckerBoard () {
                if (frontIsClear()) {
                        makeRowEast () ;
                        makeRowWest () ;
                } else {
                        moveUpAndTurnAround () ;
                }
        }

        private void makeRowEast () {
                while (facingEast()) {
                        putBeeper () ;
                        move () ;
                        if (frontIsClear () && noBeepersPresent()) {
                                move () ;
                        }
                        if (frontIsBlocked()) {
                                moveUpAndTurnAround () ;
                        }
                }
        }

        private void makeRowWest () {
                while (facingWest ()) {
                        putBeeper () ;
                        move () ;
                        if (frontIsClear () && noBeepersPresent()) {
                                move () ;
                        }
                        if (frontIsBlocked()) {
                                moveUpAndTurnAround () ;
                        }
                }
        }

        private void moveUpAndTurnAround () {
                if (frontIsBlocked()) {
                        if (facingEast ()) {
                                turnAround () ;
                                if (frontIsBlocked()) {
                                        turnRight () ;
                                        makeRowNorth () ;
                                }
                                checkForBehindBeeperWest () ;
                        }
                        if (facingWest ()) {
                                turnAround () ;
                                if (frontIsBlocked()) {
                                        turnLeft () ;
                                        makeRowNorth () ;
                                }
                                checkForBehindBeeperEast () ;
                                }
                        }
                }
        private void makeRowNorth () {
                while (frontIsClear()) {
                        move () ;
                        putBeeper () ;
                        move () ;
                }
        }

        private void checkForBehindBeeperWest () {
                move () ;
                if (beepersPresent()) {
                        turnAround () ;
                        move () ;
                        turnLeft () ;
                        move () ;
                        turnLeft () ;
                        makeRowWest () ;
                } else {
                        turnAround () ;
                        move () ;
                        putBeeper () ;
                        turnLeft () ;
                        move () ;
                        turnLeft () ;
                        move () ;
                        makeRowWest () ;
                }
        }

        private void checkForBehindBeeperEast () {
                move () ;
                if (beepersPresent()) {
                        turnAround () ;
                        move () ;
                        turnRight () ;
                        move () ;
                        turnRight () ;
                        makeRowEast () ;
                } else {
                        turnAround () ;
                        move () ;
                        putBeeper () ;
                        turnRight () ;
                        move () ;
                        turnRight () ;
                        move  () ;
                        makeRowEast () ;
                }
        }
}