Home Forums C Programming Quick Sort for a Struct Re: Re: Quick Sort for a Struct

#3499
GWILouisaxwzkla
Participant

Heres a way to do this with a doubly linked list with quicksort. This version of quicksort uses the last item in the
list as a pivot element when partitioning.



/****************************************************************
* File Name : c:programstempCG.cpp
* Date : January,6,2008
* Comments : new project
* Compiler/Assembler :
* Modifications :
*
*
*
*
*
* Program Shell Generated At: 3:51:46 p.m.
=-=-=-=-=-=-=-=--=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=*/


#include < iostream >
#include < fstream >
//#include < string.h >
//#include < conio.h >
//#include < math.h >
#include < iomanip >
#include < ctype.h >

using namespace std;

//>>>>>>>>>>>>>>>>>>>>>>>> GLOBAL DATA <<<<<<<<<<<<<<<<<<<<<<<<<

const int MAX_NAME = 50;
const int MAX_FILE_NAME = 50;
const char STOP_SYMBOL = '*';
enum keys { firstName , lastName , idNumber };
keys sortKey ;
#define OUTPUT_SPACES 15
//<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<



struct person
{

char firstName [ MAX_NAME ] ;
char lastName [ MAX_NAME ] ;
char idNumber [ MAX_NAME ] ;
person * prior;
person * next;
};


//@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ FUNCTION PROTOTYPES @@@@@@@@@@@@@@@@@@@@@@@@@@

bool readInputFile ( char * fileName , person *& frontList , person *& backList , int & itemsRead );
void quickSort ( person ** front , person ** last , int numberItems );
void swap ( person ** first , person ** last , person ** front , person ** back );
void print ( person * list );
void insertionSort ( person * list , int numberOfItems );
void destroyList ( person * list );
char * key ( person * node );

//##################################################################################


//main function ******************************

int main ( )
{

person * front , * back;
int items;

sortKey = firstName;
readInputFile ( "c:\programs\data.txt" , front , back , items );
print ( front );
quickSort ( & front , & back , items );
cout << endl << endl;
cout << "final ************************" << endl;
print ( front );
destroyList ( front );
return 0 ;
}


/******************************* FUNCTION DEFINITION ******************************

Name : readInputFile
Parameters :

fileName a(n) char * ,
frontList a(n) person *& ( person *& ) ,
backList a(n) person *& ( person *& ) ,
itemsRead a(n) int &


Returns: bool type
Comments:



++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++*/
bool readInputFile ( char * fileName , person *& frontList , person *& backList , int & itemsRead )
{


fstream inputFile;
person * temp;
char ch;
inputFile.open ( fileName ); //open input file
if ( inputFile.fail () )
{
cout << "input file did not open! " << endl;
return false;
}
temp = new person; //make new node in list
if ( temp == 0 ) //if allocation error
{
cout << "allocation error! " << endl;
return false;
}
itemsRead = 1; //start count at 1
frontList = backList = temp; //set front and back pointers to new node
temp -> prior = 0; //set new nodes prior to empty
inputFile >> temp -> firstName; //get nodes data from file
inputFile >> temp -> lastName;
inputFile >> temp -> idNumber;
ch = inputFile.peek(); //check for end of file character
while ( isspace ( ch ) ) //skip white space
{
inputFile.get();
ch = inputFile.peek();
}
while ( ch != STOP_SYMBOL ) //while not at end of file
{
temp -> next = new person; //make new item in the list
if ( temp -> next == 0 ) //check allocation
{
cout << "allocation error! " << endl;
destroyList ( frontList );
return false;
}
temp -> next -> prior = temp; //set temp to point to new node
temp -> next -> next = 0; //set next to empty
temp = temp -> next;//move list pointer to next node
backList = temp; //make new node the back of list
inputFile >> temp -> firstName; //get data
inputFile >> temp -> lastName;
inputFile >> temp -> idNumber;
ch = inputFile.peek(); //get white space
while ( isspace ( ch ) )
{
inputFile.get();
ch = inputFile.peek();
}
itemsRead ++;//count items read
}

return true;
}
/******************************* FUNCTION DEFINITION ******************************

Name : quickSort
Parameters :

front a(n) person *& ( person *& ) ,
last a(n) person *& ( person *& ) ,
numberItems a(n) int ( int )


Returns: Void type
Comments:



++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++*/
void quickSort ( person ** low , person ** high , int numberItems )
{


person * savedLow = * low; //lowt
person * savedHigh = * high;//hight
person * tempLow , * tempHigh;
person * pivot; //pivot for sorting

if ( numberItems <= 1 ) //nothing to sort
return;
if ( numberItems == 2 ) //if 2 items then swap if needed
{
tempLow = * low;
tempHigh = * high;
if ( strcmp ( key ( tempLow ) , key ( tempHigh ) ) > 0 ) //swap items if out of order
swap ( & tempLow , & tempHigh , & savedLow , & savedHigh );
* low = tempLow; //reset low and high pointers
* high = tempHigh;
return ; //end function
}



pivot = savedHigh; //make the highest element in the array the pivot
tempLow = savedLow; //start sorting at the lowest item in the list
tempHigh = ( * savedHigh ).prior; //start sorting at the second to last item
int lowCount = 1; //start counting at the first item for the low pointer
int highCount = numberItems - 1; //start counting at the second to last item for high count

do
{

//while items are less than the pivot move right
while ( lowCount <= highCount && ( strcmp ( key ( tempLow ) , key ( pivot ) ) < 0 || strcmp ( key ( tempLow ) , key ( pivot ) ) == 0 ) )
{


tempLow = tempLow -> next;
lowCount ++; //increase count of items behind pointer
if ( ! tempLow )
break;
}
//while items are greater than the pivot move right
while ( lowCount <= highCount && ( strcmp ( key ( tempHigh ) , key ( pivot ) ) > 0 || strcmp ( key ( tempLow ) , key ( pivot ) ) == 0 ) )
{


tempHigh = tempHigh -> prior;
highCount --; //decrease count of items before pointer
if ( ! tempHigh )
break;
}

if ( tempHigh ) //if top pointer has not crossed end of list , swap items
swap ( & tempLow , & tempHigh , & savedLow , & savedHigh );

} while ( lowCount <= highCount && tempHigh -> prior && tempLow -> next );

if ( tempHigh ) //if high pointer has not passed the end to the list , exchange high and low pointers
swap ( & tempLow , & tempHigh , & savedLow , & savedHigh );

//put pivot in middle of large item and small item lists
tempHigh = savedHigh;
swap ( & tempLow , & tempHigh , & savedLow , & savedHigh );
//sort list of small items
quickSort ( & savedLow , & tempLow -> prior , lowCount - 1 );
//sort list of large items
quickSort ( & tempLow -> next , & savedHigh , numberItems - lowCount );
//reset low and high pointers
* low = savedLow;
* high = savedHigh;

return;
}
/******************************* FUNCTION DEFINITION ******************************

Name : swap
Parameters :

first a(n) person *& ( person *& ) ,
last a(n) person *& ( person *& )


Returns: Void type
Comments: first



++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++*/
void swap ( person ** left , person ** right , person ** front , person ** back )
{


if ( ! * left || !* right ) //if left or right pointer is null , stop
return;
if ( * left == * right )
return;
//reset the front and back pointers
if ( ( * front ) == ( * left ) ) //if left == front
{

* front = * right; //right is new front after swap
}
else if ( ( * front ) == ( * right ) ) //if right == front
{

* front = * left; //left is new front after swap
}
if ( ( * back ) == ( * left ) ) //if left == back
{

* back = * right; //right is back after swap
}
else if ( ( * back ) == ( * right ) ) //if right is back
{

* back = * left; //left is back after swap
}



person * tempN , * tempP;

tempN = ( * left ) -> next; //save left's next and prior node setting
tempP = ( * left ) -> prior;

//case 1: right node follows left in list
if ( ( * right ) -> prior == * left )
{
( * left ) -> prior = ( * right ); //right is left's new prior node
( * left ) -> next = ( * right ) -> next; //left's next node is right's old prior node
if ( ( * left ) -> next ) //if left had a next node
( * left ) -> next -> prior = ( * right ); //set that nodes prior to right
( * right ) -> next = ( * left ); //right's next now is left
( * right ) -> prior = tempP; //right's new prior is left's old prior
if ( tempP ) //if left's old prior is not null
tempP -> next = ( * right ); //left's old prior's next is right
}
//case 2: left follows right in the list
else if ( ( * left) -> prior == ( * right ) )
{
( * left ) -> prior = ( * right ) -> prior; //left's prior is now right's prior
( * left ) -> next = ( * right ); //left's next is now right
if ( ( * right ) -> prior ) //if right's prior is not null
( * right ) -> prior -> next = ( * left ); //set its next to left
( * right ) -> prior = ( * left ); //right comes after left node now
( * right ) -> next = tempN; //right's next is left's old next
if ( tempN ) //if left's old next is non-null
tempN -> prior = ( * right ); //set its prior to right
}
//case 3: the two nodes are seperated by other nodes
else
{
( * left ) -> prior = ( * right ) -> prior; //left's prior equal's right's
( * left ) -> next = ( * right ) -> next; //left's next equal's right's

if ( ( * right ) -> next ) //if right's next is non-null
( * right ) -> next -> prior = ( * left ); //set it's prior to left
if ( ( * right ) -> prior )//if right's prior is non-null
( * right ) -> prior -> next = ( * left ); //it's next now equals left
( * right ) -> prior = tempP; //right's prior now == left's
( * right ) -> next = tempN; //right's next now == left's
if ( tempP ) //if left's prior was non-null
tempP -> next = ( * right ); //set its next to right
if ( tempN ) //if left's next was non-null
tempN -> prior = ( * right );//set its prior to right
}


person * temp = ( * left ); //swap left and right pointers to save
person * temp2 = ( * right );//position of pointers in the list
( * left ) = temp2;
( * right ) = temp;

return;
}
/******************************* FUNCTION DEFINITION ******************************

Name : print
Parameters :

list a(n) person * ( person * )


Returns: Void type
Comments:



++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++*/
void print ( person * list )
{

cout << endl;

cout << setiosflags ( ios::left );
cout << setw ( OUTPUT_SPACES ) << "first name"
<< setw ( OUTPUT_SPACES ) << "last name"
<< setw ( OUTPUT_SPACES ) << "id number" << endl << endl;
while ( list ) //while not at the end of the list
{
//output name ect....
cout << setw ( OUTPUT_SPACES ) << list -> firstName << " " << setw ( OUTPUT_SPACES ) << list -> lastName << " " << setw ( OUTPUT_SPACES ) << list -> idNumber << endl;
list = list -> next;

}

return;
}

/******************************* FUNCTION DEFINITION ******************************

Name : destroyList
Parameters :

list a(n) person * ( person * )


Returns: Void type
Comments:



++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++*/
void destroyList ( person * list )
{

person * temp;

while ( list ) //for each item in the list , destroy the list
{
temp = list;
list = list -> next;
delete temp;
}


return;
}
/******************************* FUNCTION DEFINITION ******************************

Name : key
Parameters :

first a(n) person * ( person * ) ,
second a(n) person * ( person * )


Returns: char type
Comments: use a macro for this......



++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++*/
char * key ( person * node )
{

switch ( sortKey )
{
case firstName:
return node -> firstName;
case lastName:
return node -> lastName;
case idNumber:
return node -> idNumber;

};


}

input:


bob johns 222
suzie barker 333
adam west 555
zack wilde 111
janet woods 444
qubert johns 666
barak obama 777
carly simon 888
curt cobain 999
tom gadja 1010
larry bear 1111
pilar nuffer 1212
mikey scalcee 1313
old puff 1414
charolette phifer 1515
don dokken 46464
adam ant 555
willodean mcqueen 222
*

output ( sorting with first name as key ):


first name last name id number

adam ant 555
adam west 555
barak obama 777
bob johns 222
carly simon 888
charolette phifer 1515
curt cobain 999
don dokken 46464
janet woods 444
larry bear 1111
mikey scalcee 1313
old puff 1414
pilar nuffer 1212
qubert johns 666
suzie barker 333
tom gadja 1010
willodean mcqueen 222
zack wilde 111
Press any key to continue