Program to sort a linked list by readjusting the links.

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

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

void getdata( ) ;
void append ( struct node **q, int num ) ;
void displaylist( ) ;
void selection_sort( ) ;
void bubble_sort( ) ;

void main( )
{
getdata( ) ;
clrscr( ) ;
printf ( "\nLinked List Before Sorting:\n" ) ;
displaylist( ) ;

selection_sort( ) ;
printf ( "\nLinked List After Selection Sorting:\n" ) ;
displaylist( ) ;
getch( ) ;

getdata( ) ;
clrscr( ) ;
printf ( "\nLinked List Before Sorting:\n" ) ;
displaylist( ) ;

bubble_sort( ) ;
printf ( "\nLinked List After Bubble Sorting:\n" ) ;
displaylist( ) ;
getch( ) ;
}

void getdata( )
{
int val, n ;
char ch ;
struct node *newnode;

clrscr( ) ;

newnode = NULL ;
do
{
printf ( "\nEnter a value: " ) ;
scanf ( "%d", &val ) ;

append ( &newnode, val ) ;

printf ( "\nAny More Nodes (Y/N): " ) ;
ch = getche( ) ;
} while ( ch == 'y' || ch == 'Y' ) ;

start = newnode ;
}

/* adds a node at the end of a linked list */
void append ( struct node **q, int num )
{
struct node *temp ;
temp = *q ;

if ( *q == NULL ) /* if the list is empty, create first node */
{
*q = malloc ( sizeof ( struct node ) ) ;
temp = *q ;
}
else
{
/* go to last node */
while ( temp -> link != NULL )
temp = temp -> link ;

/* add node at the end */
temp -> link = malloc ( sizeof ( struct node ) ) ;
temp = temp -> link ;
}

/* assign data to the last node */
temp -> data = num ;
temp -> link = NULL ;
}

/* displays the contents of the linked list */
void displaylist( )
{
visit = start ;

/* traverse the entire linked list */
while ( visit != NULL )
{
printf ( "%d ", visit -> data ) ;
visit = visit -> link ;
}
}

void selection_sort( )
{
struct node *p, *q, *r, *s, *temp ;

p = r = start ;
while ( p -> link != NULL )
{
s = q = p -> link ;
while ( q != NULL )
{
if ( p -> data > q -> data )
{
if ( p -> link == q ) /* Adjacent Nodes */
{
if ( p == start )
{
p -> link = q -> link ;
q -> link = p ;

temp = p ;
p = q ;
q = temp ;

start = p ;
r = p ;
s = q ;
q = q -> link ;
}
else
{
p -> link = q -> link ;
q -> link = p ;
r -> link = q ;

temp = p ;
p = q ;
q = temp ;

s = q ;
q = q -> link ;
}
}
else
{
if ( p == start )
{
temp = q -> link ;
q -> link = p -> link ;
p -> link = temp ;

s -> link = p ;

temp = p ;
p = q ;
q = temp ;

s = q ;
q = q -> link ;
start = p ;
}
else
{
temp = q -> link ;
q -> link = p -> link ;
p -> link = temp ;

r -> link = q ;
s -> link = p ;

temp = p ;
p = q ;
q = temp ;

s = q ;
q = q -> link ;
}
}
}
else
{
s = q ;
q = q -> link ;
}
}
r = p ;
p = p -> link ;
}
}

void bubble_sort( )
{
struct node *p, *q, *r, *s, *temp ;
s = NULL ;

/* r precedes p and s points to the node up to which comparisons are to be made */
while ( s != start -> link )
{
r = p = start ;
q = p -> link ;

while ( p != s )
{
if ( p -> data > q -> data )
{
if ( p == start )
{
temp = q -> link ;
q -> link = p ;
p -> link = temp ;

start = q ;
r = q ;
}
else
{
temp = q -> link ;
q -> link = p ;
p -> link = temp ;

r -> link = q ;
r = q ;
}
}
else
{
r = p ;
p = p -> link ;
}
q = p -> link ;
if ( q == s )
s = p ;
}
}
}