File program to read in reverse order the contents of a file.

[Prabhat Routray]

it's urgent, i've my exam tomorrow. please correct the errors. i've done so far.


#include<iostream>
#include<fstream>
#include<cstdlib>
#include<iomanip>
using namespace std;

int main()
{
ifstream fin; char ch; int size=0;
fin.open("txtfile.txt");
if(!fin)
{
cout<<"\nFile Opening Error...";
exit(1);
}
cout<<"\nContents of file in original order:\n";
while((ch = fin.get())!= EOF)
{
cout.put(ch);
size++;
}
cout<<"\nContents of file in reverse order:\n";
cout<<endl<<size<<endl;

fin.seekg(size,ios::end);

while(fin)
{
ch=fin.get();
cout.put(ch);
size--;
fin.seekg(size);
}
fin.close();

cin.setf(ios::unitbuf);
cin.get();
return 0;
}

[bugbyte]

Since you don't name any errors, for me personally, there are no errors to correct.

[Prabhat Routray]

hello, bugbyte
it doesnot print the reverse order.

[JLBorges]

Make one pass forward through the file, pushing each character read to a stack.
For the reverse order, pop characters one by one from the stack.

#include<iostream>
#include<fstream>
//#include<cstdlib>
//#include<iomanip>
#include <stack> // *** added
// using namespace std;

int main()
{
    std::ifstream fin( __FILE__ /* "txtfile.txt" */ );
    if( !fin.is_open() )
    {
        std::cerr << "\nFile Opening Error...\n";
        return 1 ;
    }
    std::stack<char> stk ;

    std::cout << "\nContents of file in original order:\n";
    char ch;
    while( fin.get(ch) ) // canonical
    {
        std::cout << ch ;
        stk.push(ch) ;
    }
    // note: the stream is in a failed/eof state here.
    // we don't need it any more, but if we did, 
    // we would have to first clear the state before using it
    // see: http://en.cppreference.com/w/cpp/io/basic_ios/clear
    

    std::cout << "\n\n=================\n\nContents of file in reverse order:\n";
    while( !stk.empty() )
    {
        std::cout << stk.top() ;
        stk.pop() ;
    }
    std::cout << '\n' ;
}

http://coliru.stacked-crooked.com/a/be1ead492a9434b6

[Prabhat Routray]

Thank you JLBorges.

[bugbyte]

edit: nvm, what I posted was wrong.