mattbarackman · September 12, 2012 03:24 · Sep 12, 2012
diff --git a/MidpointFindingKarel.java b/MidpointFindingKarel.java
@@ -0,0 +1,167 @@
+/*
+ * 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.
+ * Matt Barackman
+ * 9.3.2012
+ */
+
+import stanford.karel.*;
+
+public class MidpointFindingKarel extends SuperKarel {
+
+	/* METHOD: run()
+	 * 
+	 * The general strategy is to have Karel drop beeper at either
+	 * end of the first row and keep working his way towards the
+	 * center dropping beepers closer and closer until his lines of
+	 * beepers extending from both ends finally meet. He will at
+	 * that point be standing on the (or one of the two) center
+	 * columns. Next he will stating clearing the rest of the beepers,
+	 * by walking towards the right wall picking up all the beepers.
+	 * Then turning around and walking till he reaches the first
+	 * beeper (the center) and cleaning up all the beepers to the
+	 * left of that beeper. Than he simply turns around and walks back
+	 * to the center.
+	 * 
+	 * pre-condition: 
+	 * Karel is in the bottom-left corner of the window facing East.
+	 * 
+	 * post-condition:
+	 * Karel is now standing on top of a lone beeper in the center 
+	 * of the bottom row (or in one of the two center columns if
+	 * there are an even number of columns.)
+	 * 
+	 */
+
+	public void run() {
+		putBeeper();
+		walkToWall();
+		putBeeper();
+		turnAround();
+		walkToBeeper();
+		while (noBeepersPresent()){
+			putBeeper();
+			turnAround();
+			walkToBeeper();
+		}
+		clearRightOfCenter();
+		clearLeftOfCenter();
+		turnAround();
+		walkToBeeper();
+		move();
+
+	}
+
+	/* METHOD: clearRightOfCenter()
+	 * 
+	 * This will clear all Beepers to the right of the Center.
+	 * 
+	 * pre-condition: 
+	 * Karel is in the middle of the grid standing on a beeper,
+	 * facing East.
+	 * 
+	 * post-condition:
+	 * Karel is standing at the far-right of the first row, having
+	 * cleared all the beepers from the center along the way.
+	 */
+
+	private void clearRightOfCenter(){
+		clearToWall();
+	}
+
+	/* METHOD: clearRightOfCenter()
+	 * 
+	 * This will clear all Beepers to the wall in whatever way
+	 * Karel is facing. There can only be one or zero beepers on
+	 * each square.
+	 * 
+	 * pre-condition: 
+	 * Karel is facing in any direction.
+	 * 
+	 * post-condition:
+	 * Karel has now travelled to the wall and has cleared all
+	 * beepers along the way. 
+	 */
+
+	private void clearToWall(){
+		while (frontIsClear()){
+			move();
+			if (beepersPresent()){
+				pickBeeper();
+			}
+		}
+	}	
+
+	/* METHOD: clearLeftOfCenter()
+	 * 
+	 * Karel will turn around, walk to the center beeper, than
+	 * walk to the left wall clearing all the beepes along
+	 * the way. 
+	 *  
+	 * pre-condition: 
+	 * Karel is at the far right corner of bottom row facing East
+	 * with no beepers between Karel and the center beeper.
+	 * 
+	 * post-condition:
+	 * Karel is standing at the far-left corner of the first row, 
+	 * facing west, having cleared all the beepers from the center 
+	 * to the left wall. There is no only one beeper in the center
+	 * of the bottom row.
+	 */
+
+	private void clearLeftOfCenter(){
+		turnAround();
+		walkToBeeper();
+		move();
+		while (frontIsClear()){
+			move();
+			pickBeeper();
+		}
+	}
+
+	/* METHOD: walkToWall()
+	 * 
+	 * Facing in any direction, Karel will walk until he hits a
+	 * wall. 
+	 */
+
+	private void walkToWall(){
+		while (frontIsClear()){
+			move();
+		}
+	}
+
+	/* METHOD: walkToBeeper()
+	 * 
+	 * Facing in any direction, Karel will walk until there is a
+	 * beeper directly in front of him.
+	 */
+
+	private void walkToBeeper(){
+		move();
+		while (noBeepersPresent()){
+			move();
+		}
+		moveBackward();
+	}
+
+	/* METHOD: moveBackware()
+	 * 
+	 * Karel will move backward one square while remaining
+	 * facing in the same direction.
+	 */
+
+	private void moveBackward(){
+		turnAround();
+		move();
+		turnAround();
+	}
+
+}