1. ITEC 2620M Introduction to Data Structures
Instructor: Prof. Z. Yang
Course Website:
Office: DB 3049

2. Complexity Estimation – recurrence relations

3. Key Points Estimation of recursive algorithms Basic Data Types I
How many times?
What does it cost?
Basic Data Types I
Stacks

4. Relating Complexity Estimation to Recurrence Relations
“How many times?” is the number of recurrences – levels of recursion.
“What does it cost?” is for an entire “level” of recursion.
linear recursion
What does this recursive call cost?
binary recursion
What do all recursive calls at this “level” cost?

5. Examples
Factorial
Binary search
Mergesort
Quicksort

6. Abstract Data Types
A way to specify the functionality of an entity without worrying about its implementation
List ADT
  interface SortedList
{ public void insert (Object item);
public object remove ();
public boolean isInList (); … }

7. Stacks A stack is a “Last-In, First-Out” = “LIFO” buffer.
Only the top element of a stack is accessible.
When elements are added, they are pushed onto the top
When elements are removed, they are popped off the top
push() and pop() are the two defining functions of a stack
Example
Array-based Stacks