![Circular Array Q Data Structure
void enqueue(Object x) {
Q[back] = x
back = (back + 1) % size
}
Object dequeue() {
x = Q[front]
front = (front + 1) % size
return x
}
b c d e f
Q
0 size - 1
front back
This is pseudocode. Do not correct my semicolons.
When is the Q empty?
Are there error situations this
code will not catch?
What are some limitations of
this structure?](https://image.slidesharecdn.com/lecture1-230420051440-8660be03/85/lecture1-ppt-13-320.jpg)
![Array Stack Data Structure
S
0 size - 1
f e d c b
void push(Object x) {
assert(!is_full())
S[back] = x
back++
}
Object top() {
assert(!is_empty())
return S[back - 1]
}
back
Object pop() {
back--
return S[back]
}
bool is_full() {
return back == size
}](https://image.slidesharecdn.com/lecture1-230420051440-8660be03/85/lecture1-ppt-19-320.jpg)
lecture1.ppt
- 2. Outline • Overview of the Course • Queues • Stacks
- 3. Goals of the Course • Become familiar with some of the fundamental data structures in computer science • Improve ability to solve problems abstractly – data structures are the building blocks • Improve ability to analyze your algorithms – prove correctness – gauge (and improve) time complexity • Become modestly skilled with the UNIX operating system and X-windows (you’ll need this in upcoming courses)
- 4. Observation • All programs manipulate data – programs process, store, display, gather – data can be information, numbers, images, sound • Each program must decide how to store data • Choice influences program at every level – execution speed – memory requirements – maintenance (debugging, extending, etc.)
- 5. What is a Data Structure? data structure -
- 6. What is an Abstract Data Type? Abstract Data Type (ADT) - 1) An opportunity for an acronym 2) Mathematical description of an object and the set of operations on the object
- 7. Data Structures : Algorithms • Algorithm – A high level, language independent description of a step-by-step process for solving a problem • Data Structure – A set of algorithms which implement an ADT
- 8. Why so many data structures? Ideal data structure: fast, elegant, memory efficient Generates tensions: – time vs. space – performance vs. elegance – generality vs. simplicity – one operation’s performance vs. another’s Dictionary ADT – list – binary search tree – AVL tree – Splay tree – Red-Black tree – hash table
- 9. Code Implementation • Theoretically – abstract base class describes ADT – inherited implementations implement data structures – can change data structures transparently (to client code) • Practice – different implementations sometimes suggest different interfaces (generality vs. simplicity) – performance of a data structure may influence form of client code (time vs. space, one operation vs. another)
- 10. ADT Presentation Algorithm • Present an ADT • Motivate with some applications • Repeat until browned entirely through – develop a data structure for the ADT – analyze its properties • efficiency • correctness • limitations • ease of programming • Contrast data structure’s strengths and weaknesses – understand when to use each one
- 11. Queue ADT • Queue operations – create – destroy – enqueue – dequeue – is_empty • Queue property: if x is enQed before y is enQed, then x will be deQed before y is deQed FIFO: First In First Out F E D C B enqueue dequeue G A
- 12. Applications of the Q • Hold jobs for a printer • Store packets on network routers • Hold memory “freelists” • Make waitlists fair • Breadth first search
- 13. Circular Array Q Data Structure void enqueue(Object x) { Q[back] = x back = (back + 1) % size } Object dequeue() { x = Q[front] front = (front + 1) % size return x } b c d e f Q 0 size - 1 front back This is pseudocode. Do not correct my semicolons. When is the Q empty? Are there error situations this code will not catch? What are some limitations of this structure?
- 14. Q Example enqueue R enqueue O dequeue enqueue T enqueue A enqueue T dequeue dequeue enqueue E dequeue
- 15. Linked List Q Data Structure b c d e f front back void enqueue(Object x) { if (is_empty()) front = back = new Node(x) else back->next = new Node(x) back = back->next } Object dequeue() { assert(!is_empty) return_data = front->data temp = front front = front->next delete temp return temp->data }
- 16. Circular Array vs. Linked List
- 17. LIFO Stack ADT • Stack operations – create – destroy – push – pop – top – is_empty • Stack property: if x is on the stack before y is pushed, then x will be popped after y is popped LIFO: Last In First Out A B C D E F E D C B A F
- 18. Stacks in Practice • Function call stack • Removing recursion • Balancing symbols (parentheses) • Evaluating Reverse Polish Notation • Depth first search
- 19. Array Stack Data Structure S 0 size - 1 f e d c b void push(Object x) { assert(!is_full()) S[back] = x back++ } Object top() { assert(!is_empty()) return S[back - 1] } back Object pop() { back-- return S[back] } bool is_full() { return back == size }
- 20. Linked List Stack Data Structure b c d e f back void push(Object x) { temp = back back = new Node(x) back->next = temp } Object top() { assert(!is_empty()) return back->data } Object pop() { assert(!is_empty()) return_data = back->data temp = back back = back->next return return_data }
- 21. Data structures you should already know • Arrays • Linked lists • Trees • Queues • Stacks