Lecture 11

Learning objectives

After this class, you should be able to:

1. Given certain operations on a deque, draw a figure that shows its state at the end of those operations.
2. Give the time complexity of the different operations on a deque.
3. Implement features of a deque.
4. Give applications where a deque can be useful.

Reading assignment

1. Section 3.8 (up to fig 3.27), class notes for deque implementation (do not use the one in the book).
2. Optional: Fall 2003 lecture notes has additional explanations on deques (chapter 9).
3. Page 137 and 138.

Exercises and review questions

• Exercises and review questions on current lecture's material
  1. Give a sequence of operations such that a deque looks as shown in the figure below. Also give the array positions corresponding to the beginning and end of the deque.

     a

     b

  2. Let us assume a deque has the following data:

     c

     d

     a

     b

     and we now try to insert an 'e'. Show how the deque will look like after this insert operation.

  3. Implement the back member function of a deque.
  4. Implement the front member function of a deque.
  5. Implement the push_back member function of a deque.
  6. Implement the pop_back member function of a deque.
  7. Implement the pop_front member function of a deque.
  8. Implement the [] operator of a deque.
  9. If a deque looked liked in the previous question, and we push_front an e, but want the new deque to look like:

     e

     a

     b

     c

     d

     then how should the push_front code be changed? Note that this is a different implementation of a deque.

• Questions on next lecture's material
  1. Assume that we perform the following operation on the rightmost figure in Fig. 4.1 (page 138): push(8); pop(); pop();. Draw the state of the stack on the conclusion of the above operations.