// now we read the list from the pre_defined input file
PeopleList = readList( PeopleList );/** * Program Filename: Lab12e2.cpp * Authur: ZHU, Xiaoqing * Created: 4/11/98 * Modified: * Description: * This program creates linked list, it reads data from file and then * at the end it deletes list. * * In this program we will insert each node into the list according the * alphabetical order of each people's last name, this will require * string comparation and traversing of the list, also the program will * show you how to insert a node into the middle of the list. */
#include <iostream.h> #include <fstream.h> #include <string.h>
/** * the input file */ #define INPUT_FILE "a:list.in"
/** * constant * the maximum length of names */ const int MAXNAME = 16;
/**
* structure People
* stores information of a person with his/her name, id and age
*/
struct People
{
char fname[MAXNAME];
char lname[MAXNAME];
int id;
int age;
};
/**
* the linklist node type
* another structure that has People as its data field and
* next as its link field
*
* using this approach we can change the content of the data field
* without modifying linklist operation
*/
struct Node
{
People people;
Node *next;
};
/** * Function prototypes */ Node* readList( Node* ); // read a list from the input file Node* readNode( ifstream& ); // read a node from the input file
/* new! */ Node* addToListInOrder( Node*, Node* ); // add a node to the list, revised /* new! */ Node* findPosition( Node*, Node* ); // search for insert position /* new! */ Node* insertAfter( Node*, Node*, Node* ); // insert a node after another
Node* deleteList( Node* ); // delete all the nodes in the list
void printList( Node* ); // print the whole list void printPeople( People& ); // print one people
void Wait(); // prompt user to press any key to continue...
/**
* main program begins
*/
int main()
{
Node *PeopleList = NULL;
// Now call readList
/**
* Function: readList
* Description: Reads the data from a file and calls function readPeople
* will create list and put those data read from the file in the list
* Parameters: list - the linked list header pointer
* Returns: the linked list with data
*/
Node* readList( Node *list )
{
ifstream cinf;
Node *newNode = NULL;
cinf.open( INPUT_FILE );
// read data now
while ( (newNode = readNode(cinf)) != NULL ) {
// Now call readNode - this is the same as before - so just show results
list = addToListInOrder( list, newNode );
// Now call new function addToListInOrder
/**
* Function: addToListInOrder
* Description: Creates linked list with data that is passed to it
* Params: list - the linked list header pointer
* newNode - a pointer to the new node
* Returns: new header pointer
*/
Node* addToListInOrder( Node *list, Node *newnode )
{
Node *prev = NULL;
prev = findPosition( list, newnode );
// Now call findPosition
/**
* Function: findPosition new!
* Description: This function will search the list for the last persion
* record in the list that is "smaller" than the new node, then
* it will return a pointer to this node. If the first node is "bigger"
* than the new one, a NULL pointer is returned; If every
* node is "smaller" a pointer to the last node is returned.
* Params: list - the header pointer of the list
* newNode - pointer to the new node
* Returns: a pointer to the previous node of insert position
*/
Node *findPosition( Node *list, Node *newNode )
{
Node *prev=NULL, *current=list;
// while the current people is "no bigger than" the new people...
while ( current!=NULL ) {
if ( strcmp( current->people.lname, newNode->people.lname ) > 0 )
return prev;
else {
prev = current;
current = prev->next;
}
}
return prev; }
// Now return to addToListInOrder
Node* addToListInOrder( Node *list, Node *newnode )
{
Node *prev = NULL;
prev = findPosition( list, newnode );
list = insertAfter( list, prev, newnode );
// Now call insertAfter
/**
* Function: insertAfter new!
* Description: This function will insert the new node into the linked
* list after the node specified
* Params: list - the header pointer
* prev - pointer to the node that we'll insert the new one after
* newNode - pointer to the new node
* Returns: the new header pointer
*/
Node* insertAfter( Node *list, Node *prev, Node *newnode )
{
if ( prev == NULL ) { newnode->next = list; list = newnode; } else { newnode->next = prev->next; prev->next = newnode; }
return list; }
// Now return to addToListInOrder, which returns to ReadList
// Now execute the loop again and reads another node
// Now call addToListInOrder the second time
Node* addToListInOrder( Node *list, Node *newnode )
{
Node *prev = NULL;
prev = findPosition( list, newnode );
// now call findPosition the second time
Node *findPosition( Node *list, Node *newNode )
{
Node *prev=NULL, *current=list;
// while the current poeple is "no bigger than" the new people...
while ( current!=NULL ) {
if ( strcmp( current->people.lname, newNode->people.lname ) > 0 )
return prev;
else {
prev = current;
current = prev->next;
}
}
return prev; }
// Now return to addToListInOrder and call insert After
Node* insertAfter( Node *list, Node *prev, Node *newnode )
{
if ( prev == NULL ) { newnode->next = list; list = newnode; } else { newnode->next = prev->next; prev->next = newnode; }
return list; }
//Now return to addToListInOrder which returns to readList
// Now call ReadNode the third time to give
//Now call addToListInOrder the third time
// which calls findPosition the third time
Node *findPosition( Node *list, Node *newNode )
{
Node *prev=NULL, *current=list;
// while the current poeple is "no bigger than" the new people...
while ( current!=NULL ) {
if ( strcmp( current->people.lname, newNode->people.lname ) > 0 )
return prev;
else {
prev = current;
current = prev->next;
}
}
return prev; }
//Now return to addToListInOrder and call InsertAfter
Node* insertAfter( Node *list, Node *prev, Node *newnode )
{
if ( prev == NULL ) { newnode->next = list; list = newnode; } else { newnode->next = prev->next; prev->next = newnode; }
return list; }
//Now return to addToListInOrder and then ReadList
// Since this is end of file - the next call to readNode will cause
readList to break out of while loop
// and return to main function with
NOTICE: the input is now in alphabetical order!!
