/** * Program Filename: Lab12e1.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. * * This program basicly is a review of last lab's content, but we * introduced the idea of dividing a linked list node into two fields, * a data field and a next pointer field, to separate the content from * the implementation. */
#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 people struct from the input file
Node* addToList( Node*, Node* ); // add a node to the list Node* deleteList( Node* ); // delete all the nodes in the list
void printList( Node* ); // print the whole list void printPeople( const People& ); // print one people
void Wait(); // prompt user to press any key to continue...
/**
* main program begins
*/
int main()
{
Node *PeopleList = NULL; // public safety issue
// now we read the list from the pre_defined input file PeopleList = readList( PeopleList );
// NOW go the function 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 go to function readNode
// Lets assume the input file "list.in" contains the following data
1234 23 John Smith 5678 43 Bob Brown 9012 32 Bill Johnson
/**
* Function: readNode
* Description: This function will read one people's data from
* the file, allocate the memory and return the node
* Notice the combination use of get and ingore in input
* Parameters: cinf - the reference to the input file
* Returns: a pointer to the new node
*/
Node* readNode( ifstream &cinf )
{
int id;
Node *newNode;
cinf >> id;
if ( !cinf.eof() ) {
newNode = new Node;
newNode->people.id = id; cinf >> newNode->people.age; cinf.ignore( 200, '\n' );
cinf.get( newNode->people.fname, MAXNAME ); cinf.ignore( 200, '\n' );
cinf.get( newNode->people.lname, MAXNAME ); cinf.ignore( 200, '\n' );
newNode->next = NULL;
return newNode;
} else {
return NULL;
}
}
// NOW return to readList function
Node* readList( Node *list )
{
ifstream cinf;
Node *newNode = NULL;
cinf.open( INPUT_FILE );
// read data now
while ( (newNode = readNode(cinf)) != NULL ) {
//------>> return here
list = addToList( list, newNode );
//NOW call addToList
/**
* Function: addToList
* Description: Creates a new node and add it to the head of the linked
* list
* Params: list - the linked list header pointer
* newnode - a pointer to the new node
* Returns: the new header pointer
*/
Node* addToList( Node *list, Node *newnode )
{
Node *newheader;
newnode->next = list; // add to the head newheader = newnode;
return newheader; }
// NOW return to readList
Node* readList( Node *list )
{
ifstream cinf;
Node *newNode = NULL;
cinf.open( INPUT_FILE );
// read data now
while ( (newNode = readNode(cinf)) != NULL ) {
list = addToList( list, newNode );
}
// Now do loop again - call readNode a second time
Node* readNode( ifstream &cinf )
{
int id;
Node *newNode;
cinf >> id;
if ( !cinf.eof() ) {
newNode = new Node;
newNode->people.id = id; cinf >> newNode->people.age; cinf.ignore( 200, '\n' );
cinf.get( newNode->people.fname, MAXNAME ); cinf.ignore( 200, '\n' );
cinf.get( newNode->people.lname, MAXNAME ); cinf.ignore( 200, '\n' );
newNode->next = NULL;
return newNode;
} else {
return NULL;
}
}
// NOW return to readList
Node* readList( Node *list )
{
ifstream cinf;
Node *newNode = NULL;
cinf.open( INPUT_FILE );
// read data now
while ( (newNode = readNode(cinf)) != NULL ) {
list = addToList( list, newNode );
// Now call addToList a second time
Node* addToList( Node *list, Node *newnode )
{
Node *newheader;
newnode->next = list; // add to the head newheader = newnode;
return newheader; }
// Now return to readList
Node* readList( Node *list )
{
ifstream cinf;
Node *newNode = NULL;
cinf.open( INPUT_FILE );
// read data now
while ( (newNode = readNode(cinf)) != NULL ) {
list = addToList( list, newNode );
}
// Now do loop again can call readNode a third time
// but I won't repeat the code - just show the picture
// returning to readList we have
// now call addToList the third time
Node* addToList( Node *list, Node *newnode )
{
Node *newheader;
newnode->next = list; // add to the head newheader = newnode;
return newheader; }
cinf.close();
return list; }
// Now return to readList again
If this was the end of file, the next call to readNode, would detect this after trying to input and it would return NULL
This would cause readList to break out of its loop, close the file and return a pointer to the beginning of the list.
Returning back to the main function
int main()
{
Node *PeopleList = NULL; // public safety issue
// now we read the list from the pre_defined input file PeopleList = readList( PeopleList );
// we print the list to view its data after reading printList( PeopleList ); Wait(); // now we flush the list PeopleList = deleteList( PeopleList ); // then print the list again printList( PeopleList );
// now delete the whole list return 0; }