The Sorted Linked List

A sorted linked list is a linear collection of self-referential structures, called nodes, connected by pointer links, where the nodes are kept in sorted order by the values found in a particular data member, known as the key. A sorted linked list, like a general linked list is accessed by keeping a pointer to the first node of the list. This pointer to the first node of a list is typically named head. Subsequent nodes are accessed via a link pointer member that is stored in each node. Additions of nodes to a sorted linked list, require that the node is placed in the correct position to keep the list in order by the key.

The operations on linked lists include :

creation of a node
getting data
setting data into a node
adding a node to the list
deleting a node from the list
is the list empty
printing the list

The sorted linked list user interface :

/*************************************************\ * Filename: sortedll.h * * Author: Sue Bogar * * Date Written: 4/22/98 * * Date Modified: 11/22/98 * * Section: 101 * * SSN: 123-45-6789 * * EMail: bogar@cs.umbc.edu * * * * Description: This header file contains the * * structure definition for a node type, to be * * used as the nodes of a linked list, and the * * function prototypes for the functions defined * * in sortedll.c, the linked list implementation * * of the sorted linked list ADT. * \*************************************************/ #ifndef _sortedll_h #define _sortedll_h /**************** * This typedef allows us to call the type * of a pointer to a node a NODEPTR *****************/ typedef struct node *NODEPTR; /***************** * This struct, typedefed to be of type info, is meant * to store all the data about cars in a parking lot. *****************/ typedef struct info { char tagNo[8]; char owner[25]; char make[15]; char model[15]; int lot; } INFO; /***************** * The sorted linked list is implemented as * a structure that has two members, the first to * to hold data (in this case a struct of type info) * and the second member is of type NODEPTR which * holds a pointer to the next node of the list. * This pointer is known as the a link of the * linked list. *****************/ typedef struct node { INFO data; NODEPTR next; } NODE; /*****************************************************/ /****************** * CreateNode mallocs the space needed to * hold a struct of type node, initializes * the members, and returns a pointer to * the new node. ******************/ NODEPTR CreateNode (void); /****************** * GetData gets the data about a * particular vehicle that is assigned * to a parking lot, from the user and * stores it in an struct of type INFO ******************/ INFO GetData (void); /****************** * SetData places the values * found in the info structure * passed to it into the * node pointed to by the NODEPTR it * receives as an argument. ******************/ void SetData (NODEPTR temp, INFO new); /****************** * Insert takes a pointer to a NODEPTR, the * address of head, and a NODEPTR, temp, as * arguments. temp is a pointer to the * node to be inserted. The node is then * inserted into the list at the appropriate * place to maintain the list as a sorted list. ******************/ void Insert (NODEPTR* headPtr, NODEPTR temp); /****************** * Delete takes a pointer to a NODEPTR as its * first argument, which is the address of head. * Its second argument is a struct of type info, * which contains the license plate tag number to * be removed. The third argument is the string * in which to store a message. This function * traverses the list until the node containing the * target tagNo is found. That node is then deleted * from the list and a message returned stating that * fact. If the target tagNo is not in the list and * a message is returned that it was not found. ******************/ int Delete (NODEPTR* headPtr, char* target); /****************** * IsEmpty takes a NODEPTR as its first * argument, which is a pointer to the * first node in the list, commonly * known as head. It determines whether the * list is empty or not and returns 1 (true) * if the list is empty and 0 (false) if it * is not empty. ******************/ int IsEmpty (NODEPTR head); /****************** * PrintList takes a NODEPTR as an argument * which is a pointer to the first node in * the list, commonly known as head. * he list is traversed and the values * of each of the data members of each node are * printed. ******************/ void PrintList (NODEPTR head); #endif

Thursday, 17-Jan-2002 13:52:32 EST