Minor bug fixes

Author: RodneyShag

src/chapter03/MyQueue.java

@@ -25,15 +25,19 @@ public T dequeue(){
 	}
 
 	public T peek(){
-		shiftStacks();
+		if (size() == 0)
+			return null;
+		if (stack2.isEmpty())
+			shiftStacks();
 		return stack2.peek();
 	}
 
-	/* Great helper function */
 	private void shiftStacks(){
-		while (!stack1.isEmpty()){
-			T temp = stack1.pop();
-			stack2.push(temp);
+		if (stack2.isEmpty()){ // shifting items while stack2 has elements in it would mess up our queue's ordering
+			while (!stack1.isEmpty()){
+				T temp = stack1.pop();
+				stack2.push(temp);
+			}
 		}
 	}
 }

src/chapter18/EighteenPoint09.java

@@ -11,8 +11,8 @@
  *			maxheap.size()-1 == minheap.size() always holds.
  */
 public class EighteenPoint09 {	//code from website
-	private static PriorityQueue<Integer> maxHeap = new PriorityQueue<Integer>(50, Collections.reverseOrder());	// maxHeap contains all SMALL elements
-	private static PriorityQueue<Integer> minHeap = new PriorityQueue<Integer>(50);								// minHeap contains all LARGE elements
+	private static PriorityQueue<Integer> maxHeap = new PriorityQueue<Integer>(Collections.reverseOrder());	// maxHeap contains all SMALL elements
+	private static PriorityQueue<Integer> minHeap = new PriorityQueue<Integer>();						    // minHeap contains all LARGE elements
 
 	public static void addNum(int n) {
 		if (maxHeap.isEmpty())