C Program to implement a circular queue as a linked list

Here's a simple C Program to implement a circular queue as a linked list





#include < stdio.h >
#include < conio.h >
#include < alloc.h >

/* structure containing a data part and link part */
struct node
{
int data ;
struct node * link ;
} ;

void addcirq ( struct node **, struct node **, int ) ;
int delcirq ( struct node **, struct node ** ) ;
void cirq_display ( struct node * ) ;

void main( )
{
struct node *front, *rear ;

front = rear = NULL ;

addcirq ( &front, &rear, 10 ) ;
addcirq ( &front, &rear, 17 ) ;
addcirq ( &front, &rear, 18 ) ;
addcirq ( &front, &rear, 5 ) ;
addcirq ( &front, &rear, 30 ) ;
addcirq ( &front, &rear, 15 ) ;

clrscr( ) ;

printf ( "Before deletion:\n" ) ;
cirq_display ( front ) ;

delcirq ( &front, &rear ) ;
delcirq ( &front, &rear ) ;
delcirq ( &front, &rear ) ;

printf ( "\n\nAfter deletion:\n" ) ;
cirq_display ( front ) ;
}

/* adds a new element at the end of queue */
void addcirq ( struct node **f, struct node **r, int item )
{
struct node *q ;

/* create new node */
q = malloc ( sizeof ( struct node ) ) ;
q - > data = item ;

/* if the queue is empty */
if ( *f == NULL )
*f = q ;
else
( *r ) - > link = q ;

*r = q ;
( *r ) - > link = *f ;
}

/* removes an element from front of queue */
int delcirq ( struct node **f, struct node **r )
{
struct node *q ;
int item ;

/* if queue is empty */
if ( *f == NULL )
printf ( "queue is empty" ) ;
else
{
if ( *f == *r )
{
item = ( *f ) - > data ;
free ( *f ) ;
*f = NULL ;
*r = NULL ;
}
else
{
/* delete the node */
q = *f ;
item = q - > data ;
*f = ( *f ) - > link ;
( *r ) - > link = *f ;
free ( q ) ;
}
return ( item ) ;
}
return NULL ;
}

/* displays whole of the queue */
void cirq_display ( struct node *f )
{
struct node *q = f, *p = NULL ;

/* traverse the entire linked list */
while ( q != p )
{
printf ( "%d\t", q - > data ) ;

q = q - > link ;
p = f ;
}
}

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Sorting a Structure of Multiple Keys

C Program that accepts a set of 5 records for students -

Ask user to enter name, age and height of a student. Sort these records in ascending order of their names. If the names are alike then sort according to their age.

/* Sorting of a structure of multiple keys. */

#include  < stdio.h >

#include  < conio.h >

#include  < string.h >

struct stud

{

      char name[25] ;

      int age ;

      float height ;

} ;

void main( )

{

      int i, j, choice ;

      struct stud s[5], temp ;

      float ff ( float ) ;

      clrscr( ) ;

      printf ( "Enter student's name, age and height in cm :-\n") ;

      for ( i = 0 ; i  < = 4 ; i++ )

      {

            fflush ( stdin ) ;

            gets ( s[i].name ) ;

            scanf ( "%d %f", &s[i].age, &s[i].height ) ;

      }

      clrscr( ) ;

      for ( i = 0 ; i  < = 3 ; i++ )

      {

            for ( j = 0 ; j  < = 3 - i ; j++ )

            {

                  if ( strcmp ( s[j].name, s[j + 1].name )  > = 0 )

                  {

                        if ( strcmp ( s[j].name, s[j + 1].name ) == 0 )

                        {

                              if ( s[j].age  >  s[j + 1].age )

                              {

                                    temp = s[j] ;

                                    s[j] = s[j + 1] ;

                                    s[j + 1] = temp ;

                              }

                        }

                        else

                        {

                              temp = s[j] ;

                              s[j] = s[j + 1] ;

                              s[j + 1] = temp ;

                        }

                  }

            }

      }

      printf ( "Records after sorting :-\n") ;

      printf ( "Students Name\t\tAge Height\n" ) ;

      for ( i = 0 ; i  < = 4 ; i++ )

      {

            printf ( "%-20s %2d %.2f\n", s[i].name, s[i].age, s[i].height ) ;

      }

      getch( ) ;

}

float ff ( float f )

{

      float *f1 = &f ;

    return *f1 ;

}

So, how is that for a Tutorial?