Source Code : Program to maintain a linked list

_{Program to maintain a linked list}

_#include

_#include

_#include

_{/* structure containing a data part and link part */}

_{struct node}

_{

  _{int data ;}

  _{struct node * link ;}

_{} ;}

_{void append ( struct node **, int ) ;}

_{void addatbeg ( struct node **, int ) ;}

_{void addafter ( struct node *, int, int ) ;}

_{void display ( struct node * ) ;}

_{int count ( struct node * ) ;}

_{void delete ( struct node **, int ) ;}

_{void main( )}

_{

  _{struct node *p ;}

  _{p = NULL ;  /* empty linked list */}

  _{printf ( "\nNo. of elements in the Linked List = %d", count ( p ) ) ;}

  _{append ( &p, 14 ) ;}

  _{append ( &p, 30 ) ;}

  _{append ( &p, 25 ) ;}

  _{append ( &p, 42 ) ;}

  _{append ( &p, 17 ) ;}

  _{display ( p ) ;}

  _{addatbeg ( &p, 999 ) ;}

  _{addatbeg ( &p, 888 ) ;}

  _{addatbeg ( &p, 777 ) ;}

  _{display ( p ) ;}

  _{addafter ( p, 7, 0 ) ;}

  _{addafter ( p, 2, 1 ) ;}

  _{addafter ( p, 5, 99 ) ;}

  _{display ( p ) ;}

  _{printf ( "\nNo. of elements in the Linked List = %d", count ( p ) ) ;}

  _{delete ( &p, 99 ) ;}

  _{delete ( &p, 1 ) ;}

  _{delete ( &p, 10 ) ;}

  _{display ( p ) ;}

  _{printf ( "\nNo. of elements in the Linked List = %d", count ( p ) ) ;}

_}

_{/* adds a node at the end of a linked list */}

_{void append ( struct node **q, int num )}

_{

  _{struct node *temp, *r ;}

  _{if ( *q == NULL ) /* if the list is empty, create first node */}

  _{

  _{temp = malloc ( sizeof ( struct node ) ) ;}

  _{temp -> data = num ;}

  _{temp -> link = NULL ;}

  _{*q = temp ;}

  _}

  _else

  _{

  _{temp = *q ;}

  _{/* go to last node */}

  _{while ( temp -> link != NULL )}

  _{temp = temp -> link ;}

  _{/* add node at the end */}

  _{r = malloc ( sizeof ( struct node ) ) ;}

  _{r -> data = num ;}

  _{r -> link = NULL ;}

  _{temp -> link = r ;}

  _}

_}

_{/* adds a new node at the beginning of the linked list */}

_{void addatbeg ( struct node **q, int num )}

_{

  _{struct node *temp ;}

  _{/* add new node */}

  _{temp = malloc ( sizeof ( struct node ) ) ;}

  _{temp -> data = num ;}

  _{temp -> link = *q ;}

  _{*q = temp ;}

_}

_{/* adds a new node after the specified number of nodes */}

_{void addafter ( struct node *q, int loc, int num )}

_{

  _{struct node *temp, *r ;}

  _{int i ;}

  _{temp = q ;}

  _{/* skip to desired portion */}

  _{for ( i = 0 ; i < loc ; i++ )}

  _{

  _{temp = temp -> link ;}

  _{/* if end of linked list is encountered */}

  _{if ( temp == NULL )}

  _{

  _{printf ( "\nThere are less than %d elements in list", loc ) ;}

  _{return ;}

  _}

  _}

  _{/* insert new node */}

  _{r = malloc ( sizeof ( struct node ) ) ;}

  _{r -> data = num ;}

  _{r -> link = temp -> link ;}

  _{temp -> link = r ;}

_}

_{/* displays the contents of the linked list */}

_{void display ( struct node *q )}

_{

  _{printf ( "\n" ) ;}

  _{/* traverse the entire linked list */}

  _{while ( q != NULL )}

  _{

  _{printf ( "%d ", q -> data ) ;}

  _{q = q -> link ;}

  _}

_}

_{/* counts the number of nodes present in the linked list */}

_{int count ( struct node * q )}

_{

  _{int c = 0 ;}

  _{/* traverse the entire linked list */}

  _{while ( q != NULL )}

  _{

  _{q = q -> link ;}

  _{c++ ;}

  _}

  _{return c ;}

_}

_{/* deletes the specified node from the linked list */}

_{void delete ( struct node **q, int num )}

_{

  _{struct node *old, *temp ;}

  _{temp = *q ;}

  _{while ( temp != NULL )}

  _{

  _{if ( temp -> data == num )}

  _{

  _{/* if node to be deleted is the first node in the linked list */}

  _{if ( temp == *q )}

  _{*q = temp -> link ;}

  _{/* deletes the intermediate nodes in the linked list */}

  _else

  _{old -> link = temp -> link ;}

  _{/* free the memory occupied by the node */}

  _{free ( temp ) ;}

  _{return ;}

  _}

  _{/* traverse the linked list till the last node is reached */}

  _else

  _{

  _{old = temp ;  /* old points to the previous node */}

  _{temp = temp -> link ;  /* go to the next node */}

  _}

  _}

  _{printf ( "\nElement %d not found", num ) ;}

_}