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Program 8 :Write a C++ program to read k Lists of names and merge them using kway merge algorithm with k = 8.

#include<iostream.h>
#include<fstream.h>
#include<string.h>

// Record specification

class record
{
public: char name[20];
char usn[20];

}rec[20];

int no;

fstream file[8];

//The first 8 files

char fname[8][8] = {“l.txt”,”2.txt”,”3.txt”,”4.txt”,”5.txt”,”6.txt”,”7.txt”,”8.txt”};

void merge_file(char* file1, char* file2, char* filename)
{
record recrd[20];
int k; k=0;
fstream f1,f2;
f1.open(file1,ios::in);   //open the first file
f2.open(file2,ios::in);   //open the second file
while(!f1.eof()) //Unpack and retrieve first file
{
f1.getline(recrd[k].name,20,’|’);
f1.getline(recrd[k++].usn,20,’n’);
}
while(!f2.eof()) //Unpack and retrieve second file
{
f2.getline(recrd[k].name,20,’|’);
f2.getline(recrd [k++].usn, 20,’n’);
}
record temp;
int t,y;
for(t=0;t<k-2;t++) //Sort the retrieved records
for(y=0;y<k-t-2;y++)
if(strcmp(recrd[y].name,recrd[y+1].name)>0)
{
temp=recrd[y];
recrd[y]=recrd[y+1];
recrd[y+1]=temp;
}
fstream temp1;
temp1.open(filename,ios::out);      //Open the file to be packed into
for(t=1;t<k-1;t++) //Pack the sorted records onto the file
temp1<<recrd[t].name<<“|”<<recrd[t].usn<<“n”;
f1.close();
f2.close();
temp1.close();
return;
}
void kwaymerge()
{
char filename[7][20]={“ll.txt”,”22.txt”,”33.txt”,”44.txt”,”lll.txtw”,”222.txt”,”llll.txr”};
int i;
int k;
k=0;
for(i=0;i<8;i+=2) //Merge and sort the 8 original files onto
{ //the four files indicated {ll.txt,22.txt….}
merge_file(fname[i],fname[i+1],filename[k++]);
}
k=4;
for(i=0;i<4;i+=2) //Merge and sort the four files onto lll.txt and 222.txt
{
merge_file(filename[i],filename[i+1],filename[k++]);
}
//Merge and sort the two files onto the llll.txt file
merge_file(filename[4],filename[5],filename[6]);
return;
}

int main()
{
int i;
cout<<“Enter the no. of records : “;
cin>>no;
cout<<“nEnter the details : n”;
for(i=0;i<8;i++) //Create 8 files to store the split data
file[i].open(fname[i],ios::out);
for(i=0;i<no;i++) //Split and pack data onto the files
{
cout<<“Name :”; cin>>rec[i].name;
cout<<“USN  : “;cin>>rec[i].usn;
file[i%8]<<rec[i].name<<‘|'<<rec[i].usn<<“n”;
}
for(i=0;i<8;i++)
file[i].close();
kwaymerge(); //Merge
fstream result;
result.open(“llll.txt”,ios::in);
cout<<“nSorted Records : n”;
char name[20],usn[20];
for(i=0;i<no;i++) //Unpack the sorted records and dispL
{
result.getline(name,20,’|’);
result.getline(usn,20,’n’);
cout<<“nName   : “<<name<<“nUSN : “<<usn<<“n”;
}
return 0;
}