SLIDE 1
Stacks and Queues
25
Stack
LIFO: Last-in First-out
26
In/Out Push Pop
Stack
Undo/Redo Back/Forward
Function call/return
Stacks and Queues 25 Stack In/Out LIFO: Last-in First-out Push - - PowerPoint PPT Presentation
Stacks and Queues 25 Stack In/Out LIFO: Last-in First-out Push - - PowerPoint PPT Presentation
Stacks and Queues 25 Stack In/Out LIFO: Last-in First-out Push Pop Undo/Redo Back/Forward Function call/return Stack 26 Queue HPC FIFO: First-in First-out Back Front In Out Jobs Enqueue Dequeue Queue 27 Queue and Stack ADT
SLIDE 2
SLIDE 3
In Enqueue Out Dequeue
Front Back
Queue
Queue
FIFO: First-in First-out
27
HPC
Jobs
SLIDE 4
Queue and Stack ADT
Queue
Enqueue Dequeue Front Size Empty?
Stack
Push Pop Top Size Empty?
28
SLIDE 5
Stack/Queue Implementation
29
List
Push_back Pop_back Push_front Pop_front Front Back Size Empty
Stack
Push Pop Top Size Empty
Queue
Enqueue Dequeue Front Size Empty
SLIDE 6
Queue Implementation
30
Queue Array Impl. Linked List Impl.
Enqueue O(1) O(1) Dequeue O(n) O(1) Front O(1) O(1) Memory overhead Small Big Random access O(1) O(n)
SLIDE 7
Circular Array Queue
31
Front Back
SLIDE 8
Circular Array Queue
32
Front Back
Enqueue
SLIDE 9
33
Front
Dequeue
Circular Array Queue
Back
SLIDE 10
Circular Linked List Queue
34
Back Front
SLIDE 11
Queue Implementation
35
Queue Circular Array Impl. Circular Linked List Impl.
Enqueue O(1) O(1) Dequeue O(1) O(1) Front O(1) O(1) Memory overhead Small Big
SLIDE 12
Standard Template Library (STL)
Lists, stacks, and queues are all implemented in STL In a real program, you would better use them; why? For the sake of learning, you are not allowed to use STL during this class unless otherwise mentioned
36
SLIDE 13
Stack Applications
Expression evaluation Human-friendly infix expressions
The operator falls between the two operands 3 + 2 × 5 = 13 Easier to read and understand Can be easily broken into pieces
Machine-friendly postfix expressions
The operator is placed after the two operands 325 ×+= 13 Easier to compute in one pass No need for parentheses
37
SLIDE 14
Evaluate postfix expressions
Infix: 3 × 5 + 4/2 × 2 = 34 Postfix: 35 × 42/+2 ×
38
3 5 ⨉ 4 2 / + 2 ⨉
Stack of
- perands
SLIDE 15
Postfix Evaluation Example
39
3 5 ⨉ 4 2 / + 2 ⨉
Stack of
- perands
SLIDE 16
Postfix Evaluation Example
40
3 5 ⨉ 4 2 / + 2 ⨉
Stack of
- perands
3
Push
SLIDE 17
Postfix Evaluation Example
41
3 5 ⨉ 4 2 / + 2 ⨉
Stack of
- perands
3 5
Push
SLIDE 18
Postfix Evaluation Example
42
3 5 ⨉ 4 2 / + 2 ⨉
Stack of
- perands
3 5
Pop
SLIDE 19
Postfix Evaluation Example
43
3 5 ⨉ 4 2 / + 2 ⨉
Stack of
- perands
3 5
Pop
SLIDE 20
Postfix Evaluation Example
44
3 5 ⨉ 4 2 / + 2 ⨉
Stack of
- perands
3 5 ⨉
SLIDE 21
Postfix Evaluation Example
45
3 5 ⨉ 4 2 / + 2 ⨉
Stack of
- perands
15
Push
SLIDE 22
Postfix Evaluation Example
46
3 5 ⨉ 4 2 / + 2 ⨉
Stack of
- perands
15
Push
4
SLIDE 23
Postfix Evaluation Example
47
3 5 ⨉ 4 2 / + 2 ⨉
Stack of
- perands
15 4
Push
2
SLIDE 24
Postfix Evaluation Example
48
3 5 ⨉ 4 2 / + 2 ⨉
Stack of
- perands
15 4 2
SLIDE 25
Postfix Evaluation Example
49
3 5 ⨉ 4 2 / + 2 ⨉
Stack of
- perands
15 4 2
Pop Pop
/ 2
Push
SLIDE 26
Postfix Evaluation Example
50
3 5 ⨉ 4 2 / + 2 ⨉
Stack of
- perands
15 2
Pop Pop
+ 17
Push
SLIDE 27
Postfix Evaluation Example
51
3 5 ⨉ 4 2 / + 2 ⨉
Stack of
- perands
17
Push
2
SLIDE 28
Postfix Evaluation Example
52
3 5 ⨉ 4 2 / + 2 ⨉
Stack of
- perands
17 2
Pop Pop
⨉ 34
Push
SLIDE 29
Postfix Evaluation Example
53
3 5 ⨉ 4 2 / + 2 ⨉
Stack of
- perands
34
SLIDE 30
Infix to Postfix Conversion
Convert the input into a sequence of
- perators and operands
Account for operator precedence Account for parentheses Example
Infix (input): 3 × 5 + 4/2 × 2 Postfix (desired output): 35 × 42/+2 ×
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SLIDE 31
Example
55
( 3 ⨉ 5 + 4 / 2 ) ⨉ 2
Stack of
- perators
(
Input Output
SLIDE 32
Example
56
( 3 ⨉ 5 + 4 / 2 ) ⨉ 2
Stack of
- perators
(
Input Output
3
SLIDE 33
Example
57
( 3 ⨉ 5 + 4 / 2 ) ⨉ 2
Stack of
- perators
(
Input Output
3
⨉
SLIDE 34
Example
58
( 3 ⨉ 5 + 4 / 2 ) ⨉ 2
Stack of
- perators
(
Input Output
35
⨉
SLIDE 35
Example
59
( 3 ⨉ 5 + 4 / 2 ) ⨉ 2
Stack of
- perators
(
Input Output
35⨉
+
SLIDE 36
Example
60
( 3 ⨉ 5 + 4 / 2 ) ⨉ 2
Stack of
- perators
(
Input Output
35⨉4
+
SLIDE 37
Example
61
( 3 ⨉ 5 + 4 / 2 ) ⨉ 2
Stack of
- perators
(
Input Output
35⨉4
+ /
SLIDE 38
Example
62
( 3 ⨉ 5 + 4 / 2 ) ⨉ 2
Stack of
- perators
(
Input Output
35⨉42
+ /
SLIDE 39
Example
63
( 3 ⨉ 5 + 4 / 2 ) ⨉ 2
Stack of
- perators
Input Output
35⨉42/+
SLIDE 40
Example
64
( 3 ⨉ 5 + 4 / 2 ) ⨉ 2
Stack of
- perators
Input Output
35⨉42/+
⨉
SLIDE 41
Example
65
( 3 ⨉ 5 + 4 / 2 ) ⨉ 2
Stack of
- perators
Input Output
35⨉42/+2
⨉
SLIDE 42
Example
66
( 3 ⨉ 5 + 4 / 2 ) ⨉ 2
Stack of
- perators
Input Output