Stacks and Queues

1
Stacks and Queues

• 2014, Fall
• Pusan National University
• Ki-Joune Li

2
Stack

• Stack
• A Container
• Last-In First-Out (LIFO)
• Access only to the element at the top
• Push Insert an element at the top
• Pop Remove an element from the top
• Example
• Function Invocation
• Previous frame pointer (registers, local
  variables)
• Return Address, Parameters

3
Operations and Implementation

• Operations
• Maintenance creation of a new stack, deletion
  of stack
• Push and Pop
• IsEmpty and IsFull
• Data Structures

Class Stack private int top,MaxSize
Type stack// public Stack(int
size) Boolean isFull(), isEmpty()
Type pop() void push(Type element)
4
Queue

• Queue
• A Container
• First-In First-Out (FIFO)
• Access only to the elements at the front and rear
• Add Insert an element to the rear
• Delete Remove an element from the front
• Example
• Process Scheduling

rear
front
5
Operations and Implementation

• Operations
• Maintenance creation of a new queue, deletion
  of queue
• Add and Delete
• IsEmpty and IsFull
• Data Structures

Whats the problem ?
Class Queue private
int front,rear,MaxSize Type queue//
public Queue(int size) Boolean
isFull(), isEmpty() Type delete()
void add(Type element)
6
Circular Queue
Class CircularQueue private
int front,rear,MaxSize Type queue//
public Queue(int size) Type delete()
void add(Type element)
QueueQueue(int size) MaxSizesize queuenew
TypeMaxSize frontrear1
void Queuedelete(Type v) if(frontrear)
queueEmpty() else front(front1)MaxSize
return queuefront
void Queueadd(Type v) newRear(rear1)MaxSiz
e if(frontnewRear) queueFull() else
rearnewRear queuerearv
7
Example
void Queueadd(Type v) newRear(rear1)MaxSiz
e if(frontnewRear) queueFull() else
rearnewRear queuerearv
Typr Queuedelete() if(frontrear)
queueEmpty() else front(front1)MaxSize
return queuefront
front
0
1
2

MaxSize-1
3
rear
newRear
front1 rear1
front1 rear1 newRear2
front1 rear2 newRear3
front1 rearMaxSize-1 newRear0
front1 rear0 newRear1
front1 rear2
front1 rear3
front1 rear0
front2 rear0
frontMaxSize-1 rear0
front0 rear0
front0 rear0
8
Application of Stack Mazing Problem
How to find the path ?
9
Path Finding Algorithm for Mazing Problem
Algorithm PathFinding(int p,int q,int
mazepq) // (p,q) coorinates of exit cell
pathStack ? initialize Stack
pathStack.push((0,0)) while(pathStack.isEmpty()
NO) (i,j)? pathStack.getTop() // read
but not remove while(there is an unvisited
cell (m,n) from (i,j)) pathStack.push((m,n
)) if(mp and nq) // path found
pathStack.print() // pop and print
return (i,j)?(m,n)
pathStack.pop() print No path End
Algorithm PathFinding
10
Application of stack Evaluation of Expressions
How to evaluate this ?
X A / B C D E A C
X A B / C D E A C
11
Evaluation of Expression in Postfix Notation
X A B / C D E A C
C
/
A
B
-
D
E

D

T6
12
Infix to Postfix
A
/
(
B
-
C
)

D

E
-
-
-
(
(
(
(

/
/
/
/
/
/


-
A
B
C
-
/
D
E