Unterschiede

it-artikel:my-solution-on-assignment-1-problem-4 [2009-10-10 06:02] mail@awerner.homeip.net angelegt		it-artikel:my-solution-on-assignment-1-problem-4 [2009-10-10 06:12] (aktuell) mail@awerner.homeip.net
Zeile 1:		Zeile 1:
	====== My Solution on Assignment 1 - Problem 4 ======		====== My Solution on Assignment 1 - Problem 4 ======
		+	This is my Solution of Assignment 1 - Problem 4 from the [[http://see.stanford.edu/see/courseinfo.aspx?coll=824a47e1-135f-4508-a5aa-866adcae1111|Computer Science Course CS106A of Prof. Mehran Sahami]] at the [[http://www.stanford.edu|STANDFORD University]].
		+
		+	<code>
		+	/*
		+	* 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.
		+	*/
		+
		+	import stanford.karel.*;
		+
		+	public class MidpointFindingKarel extends SuperKarel {
		+
		+	public void run() {
		+	/*
		+	* Karel finds the middle (-+1) of the world and drops
		+	* a beeper there.
		+	*/
		+	checkWidth();
		+	goMiddle();
		+	putBeeper();
		+	paintCorner(RED);
		+
		+	while( beepersPresent() ) { // infinite loop (dance)
		+	paintCorner(GREEN);
		+	turnLeft();
		+	paintCorner(RED);
		+	turnLeft();
		+	}
		+	}
		+
		+	private void checkWidth() {
		+	/* this method lays a line of beepers to determine the width of his world
		+	* then it stacks/stores the beepers at 1,1
		+	*
		+	* Pre-condition: Karel at 1,1 facing EAST
		+	* no Beepers at all
		+	*
		+	* Post-condition: Karel at 1,1 facing EAST
		+	* Width of World represented as a Stack of
		+	* Beepers at 1,1
		+	*/
		+
		+	drawLine();
		+	collectBeepers();
		+	}
		+
		+
		+	private void drawLine() {
		+	/* this method lays a line of beepers to determine the width of his world
		+	*
		+	* Pre-condition: Karel at 1:1 facing EAST
		+	* no Beepers at all
		+	* Post-condition: Karel infront of RIGHT WALL (x,1) facing EAST
		+	* behind him a line of beepers
		+	*/
		+	while( frontIsClear() ) {
		+	putBeeper();
		+	move();
		+	}
		+	putBeeper();
		+	}
		+
		+	private void collectBeepers() {
		+	/* this method collects a line of beepers and stacks them
		+	* at 1,1
		+	*
		+	* Pre-condition: Karel infront of RIGHT WALL (x,1) facing EAST
		+	* behind him a line of beepers
		+	*
		+	* Post-condition: Karel at 1:1 facing EAST, sitting on a Stack of
		+	* Beepers representing the WIDTH of his World
		+	*/
		+	turnAround();
		+	while( frontIsClear() ) {
		+	while( beepersPresent() ) {
		+	pickBeeper();
		+	move();
		+	putBeeper();
		+	moveBack();
		+	}
		+	move();
		+	}
		+	turnAround();
		+	}
		+
		+	private void moveBack() {
		+	/* moves karol ONE STEP back keeping direction heading
		+	*
		+	*/
		+	turnAround();
		+	move();
		+	turnAround();
		+	}
		+
		+
		+	private void goMiddle() {
		+	/* this method moves karel (and the beepers left at his place) to the next
		+	* position, taking 2 Beepers per Step.
		+	*
		+	* Pre-condition: Karel at 1,1 facing EAST
		+	* X Beepers at 1,1
		+	*
		+	* Post-condition: Karel at x,1 (near middle) facing EAST
		+	* no beepers left
		+	*/
		+
		+	pickBeeper(); // off by one bug: need to walk x-1 steps
		+
		+	while( beepersPresent() ) {
		+	pickBeeper(); // take one beeper per Step
		+	pushStack();
		+	move();
		+	if( beepersPresent() ) { // Still Beepers left?
		+	pickBeeper(); // take one MORE beeper as charge/cost
		+	}
		+	}
		+	}
		+
		+
		+
		+	private void pushStack() {
		+	/* this method moves the whole stack of beepers on karels actual
		+	* position ONE STEP further keeping the direction.
		+	*
		+	* Pre-condition: Karel at x,1 facing EAST with
		+	* X Beepers at his position.
		+	*
		+	* Post-condition: Karel at x+1,1 facing EAST with
		+	* X-1 Beepers at his position.
		+	*/
		+
		+	while( beepersPresent() ) {
		+	pickBeeper(); // take one beeper as charge/cost
		+	move();
		+	putBeeper();
		+	moveBack();
		+	}
		+	}
		+	}
		+
		+	</code>