Array based stack fixes

Author: deepak-malik

src/com/deepak/data/structures/Stack/ArrayBasedStack.java

@@ -53,10 +53,8 @@ public Object pop() {
 		if (size == 0) {
 			throw new NoSuchElementException("Cannot delete from a empty Stack");
 		}
-		Object result = array[0];
-		for (int i = 0; i < array.length - 1; i++) {
-			array[i] = array[i + 1];
-		}
+		Object result = array[size - 1];
+		array[size - 1] = null;
 		size--;
 		return result;
 	}
@@ -70,7 +68,7 @@ public Object peek() {
 		if (size == 0) {
 			throw new NoSuchElementException("Cannot peek from a empty Stack");
 		}
-		return array[0];
+		return array[size - 1];
 	}
 
 	/**

test/com/deepak/data/structures/Stack/ArrayBasedStackTest.java

@@ -43,9 +43,9 @@ public void testPop() {
 		stack.push(35);
 		stack.push(13);
 		Assert.assertTrue(stack.size() == 4);
-		Assert.assertEquals(stack.pop(), 3);
-		Assert.assertEquals(stack.pop(), 17);
+		Assert.assertEquals(stack.pop(), 13);
 		Assert.assertEquals(stack.pop(), 35);
+		Assert.assertEquals(stack.pop(), 17);
 		Assert.assertTrue(stack.size() == 1);
 	}
 
@@ -62,11 +62,11 @@ public void testPeek() {
 		stack.push(35);
 		stack.push(13);
 		Assert.assertTrue(stack.size() == 4);
-		Assert.assertEquals(stack.peek(), 3);
+		Assert.assertEquals(stack.peek(), 13);
 		Assert.assertTrue(stack.size() == 4);
 		stack.pop();
 		Assert.assertTrue(stack.size() == 3);
-		Assert.assertEquals(stack.peek(), 17);
+		Assert.assertEquals(stack.peek(), 35);
 	}
 
 }