1. Stack and Queues Stack implementation using Array
Stack implementation using Linked List
Queue implementation using Array
Queue implementation using Linked List
Convert Infix Exp into Postfix
Evaluate Postfix Expression
Convert Postfix into Infix

2. Queue Implementation Using Linked List
Queue is a data structure in which front pointer point to front element of queue and rear pointer point to rear element of queue . It is implemented with the help of pointers and self referential structure. Each element ( also called node ) contain two fields : Information part and Pointer.
Front
struct Student {
int RollNo;
char Name[20] ;
Student * link ; }
InfoPart
Link
InfoPart
Link
Rear
InfoPart
Link
Null

3. student *Front = NULL, *Rear = NULL; void main ( ) int c ; do
struct Student {
int RollNo;
char Name[20] ;
Student * link ;
} ;
student *Front = NULL, *Rear = NULL;
void main ( )
int c ; do
clrscr( );
cout << “1.Insert\n2.Delete\n3.Show\nExit Any other number\n”;
cin>>c ;
switch ( c )
case 1 : Insert ( ) ; break ;
case 2 : Delete ( ) ; break ;
case 3 : show ( ) ; break ; }
} while(c>=1 && c<= 3);

4. Front
void Insert ( ) { //create node Student *ptr ; ptr = new Student ; if ( ptr == NULL ) // checking overflow { cout << “Overflow “ ; return ; } //assigning Values cout << “Enter RollNo “ ; cin >> ptr -> RollNo; cout << “Enter Name “ ; gets( ptr -> RollNo ) ; ptr - > link =NULL; // Insert Node (Element) if ( Front = = NULL ) { Front=Rear = ptr ; } else Rear- > link =Ptr ; Rear= ptr ; }
Rear
Null
Null
InfoPart
Link
Ptr
Null
Front
InfoPart
Link
InfoPart
Link
Rear
Null
InfoPart
Link
Null
Ptr

5. Front
void Delete ( ) { student *ptr ; if ( Front = = NULL ) { cout<<“Underflow “ ; return; } ptr=front; if (front==rear) front=rear=NULL; } else front=front - > link ; cout<<ptr->name<<“is deleted”; delete ptr ;
Null
Front
InfoPart
Link
InfoPart
Link
InfoPart
Link
Null
Rear
Ptr

6. void Display ( ) { student
void Display ( ) { student *ptr ; if ( Front = = NULL ) { cout<<“Underflow “ ; } else ptr=front; while (ptr!=NULL) cout<<“Name”<<ptr->Name<<“,”<<“RollNo”<<ptr->RollNo; ptr=ptr - > link ; }

7. Queue using Array Insert 10 Insert 20 Insert 30 Delete Insert 50 4 3
Front 30 2
Rear
Front 20 1
Rear
Front 10
Rear
Front = -1,Rear=-1 50

8. const int max=100; void main ( ) { int DATA [max ] ,Front= -1,Rear=-1, c ; do clrscr( ); cout << “1.Insert\n2.Delete\n3.Show\nExit Any other number\n”; cin>>c ; switch ( c ) case 1 : Insert ( DATA , Front, Rear) ; break ; case 2 : Delete ( DATA , Front,Rear) ; break ; case 3 : show ( DATA , Front,Rear) ; break ; } } while(c>=1 && c<= 3);

9. void Insert ( int Num [ ] , int & Front , int & Rear) { int item ; //Check overflow condition if ( Rear == max – 1 ) cout<<“Overflow “; return; } if (Rear==-1) front=rear=0; else Rear =Rear +1; cout << “Enter Item To Push into the stack\n; cin >> item; Num [ Rear ] =item; cout<<“Item Inserted “;

10. void Delete ( int Num [ ] , int &Rear, int &Front ) { //Check underflow condition if ( Front == – 1 ) cout<<“underflow “; return; } if (Front==Rear) cout << Num[ Front ]<<“is to be deleted \n“; Front= Rear =-1; else Front=Front+1;

11. void show ( int Num [ ] , int Front ,int Rear ) { //Check underflow condition if ( Front== – 1 ) cout<<“underflow “; } else for ( i= Front; i <=Rear ; i ++ ) cout<< Num [ i ] << endl ;