File Structure ( FS ) Lab Program 6 ( 6th Semester Information Science)- Alternative 1

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Program 6 : Write a C++ program to implement index on secondary key, the name, for a file of student objects. Implement add ( ), search ( ), delete ( ) using the secondary index

#include<iostream>
#include<fstream>
#include<sstream>
#include<string>
using namespace std;
class secondary_index{

public:
string Name_list[100];
int Address_list[100];
int count;
void create_index();
void insert() ;
void remove(string);
void delete_from_file(int);
void search(string);
int search_index(string);
void read_from_file(int);
string extract_Name(string);
void sort_index();

};

void secondary_index::create_index()
{
fstream file;
int pos;
string buffer,name;
count=-1;
file.open(“1.txt”,ios::in);
while(!file.eof())
{
pos=file.tellg();
buffer.erase();
getline(file,buffer);
if(buffer.empty())
break;
//imp since it leads the last n and goes to new line
name=extract_Name(buffer);
Name_list[++count]=name;
Address_list[count]=pos;
}
file.close();
sort_index();

buffer.erase();
}

string secondary_index::extract_Name(string buffer)
{string USN,Name;
int i=0;
USN.erase();
while(buffer[i]!=’|’)
USN+=buffer[i++];
Name.erase();
i++;
while(buffer[i]!=’|’)
Name+=buffer[i++];
return Name;
}

void secondary_index::sort_index()
{
int i,j,temp_Address;
string temp_Name;
for(int i=0;i<count;i++)
{
for(int j=i+1;j<=count;j++)
{
if(Name_list[i]>Name_list[j])
{
temp_Name=Name_list[i];
Name_list[i]=Name_list[j];
Name_list[j]=temp_Name;
temp_Address=Address_list[i];
Address_list[i]=Address_list[j];
Address_list[j]=temp_Address;

}

}
}
}

void secondary_index::insert()
{
string   USN,Name,Branch,sem,buffer;
int semester,pos;
fstream file ;
cout<< “n USN:”;
cin>>USN;
cout<< “n Name:”;
cin>>Name;
cout<< “nBranch:” ;
cin>>Branch;
cout<< “nSEMESTER:”;
cin>>semester;
stringstream out;
out<<semester;
sem=out.str();
buffer=USN+’|’+Name+’|’+Branch+’|’+sem+’$’+’n’;
file.open(“1.txt”,ios::out|ios::app);
pos=file.tellp();
file<<buffer;
file.close();
Name_list[++count]=Name;

Address_list[count]=pos;
sort_index();
}
int secondary_index::search_index(string key){
int low=0,high=count,mid=0,flag=0;
while(low<=high){
mid=(low+high)/2;
if(Name_list[mid]==key){
flag=1;
break;
}
if(Name_list[mid]>key)
high=mid-1;
else
low=mid+1;
}
if(flag){
return mid;
}
else
return -1;
}
void secondary_index::search(string key){
int pos=0,t;
string buffer;
buffer.erase();
pos=search_index(key);
if(pos>=0){
read_from_file(pos);
t=pos;
while(Name_list[++t]==key)
read_from_file(t);
t=pos;
while(Name_list[–t]==key)
read_from_file(t);
}
else
cout<<“n”<<“Not found”;
}
void secondary_index::read_from_file(int pos){
int address;
string buffer;
/for(int i=pos;i<count;i++){
Name_list[i]=Name_list[i+1];
Address_list[i]=Address_list[i+1];
}    */
fstream file;
file.open(“1.txt”);
address=Address_list[pos];
file.seekp(address,ios::beg);
getline(file,buffer);
cout<<endl<<“Found the record:”<<buffer;
file.close();
}
void secondary_index::remove(string key){
int pos=0,t,ch;
string buffer;
buffer.erase();
pos=search_index(key);
if(pos>=0){
read_from_file(pos);
cout<<endl<<“delete ?”;
cin>>ch;
if(ch)
delete_from_file(pos);
t=pos;
while(Name_list[++t]==key){
read_from_file(t);
cout<<endl<<“Delete?”;
cin>>ch;
if(ch)
delete_from_file(t);
}
t=pos;
while(Name_list[–t]==key){
read_from_file(t);
cout<<endl<<“Delete?”;
cin>>ch;
if(ch)
delete_from_file(t);
}
}
else
cout<<“nnNot foundn”;
}
void secondary_index::delete_from_file(int pos){
char del_ch=’‘;
int i,address;
if(pos>=0){
fstream file;
file.open(“1.txt”);
address=Address_list[pos];
file.seekp(address,ios::beg);
file.put(del_ch);
cout<<endl<<“nnRecord deleted:”;
file.close();
}
for(int i=pos;i<count;i++){
Name_list[i]=Name_list[i+1];
Address_list[i]=Address_list[i+1];
}

count–;
}
int main(){
int ch;
string key;
secondary_index i1;
i1.create_index();
while(1){
cout<<“nMain Menun1:Add()n2:Search()n3:Delete()n4:Exit()nEnter the choice”;
cin>>ch;
switch(ch){
case 1:cout<<“Data n”;
i1.insert();
break;
case 2:cout<<“Enter the namen”;
cin>>key;
i1.search(key);
break;
case 3:cout<<“Enter the Name”;
cin>>key;
i1.remove(key);
break;
case 4: return 0;
default:cout<<“Wrong Choice!!!!!!!nn”;

}
}
}