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problem reading a in reverse order

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Join Date: Jul 2008

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srisaravanavel srisaravanavel is offline

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problem reading a in reverse order

Jul 26th, 2008

The below program works fine for a input file that has only one line. but goes to an infinite loop for a multiline file. Kindly suggest.

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

void main()
{
   char data[10000];

   int i=0;

   ifstream ofile("c:\\temp\\welcome.txt");
   cout<<"File opened\n";

  // clrscr();
   
   ofile.seekg(-1,ios::end);

   while(1)

   {

    if(ofile.tellg()==-1)
    
break;
  
    i++;
    ofile.get(data[i]);


    ofile.seekg(-2,ios::cur);



  }


  data[i]='\0';

  cout<<data;


getch();

}//main

Last edited by Tekmaven; Jul 26th, 2008 at 4:39 am. Reason: Code Tags

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iamthwee

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Re: problem reading a in reverse order

Jul 26th, 2008

What are you trying to do, read each line in reverse order, or take a line and read the characters from right to left or what?

Last edited by iamthwee; Jul 26th, 2008 at 7:23 am.

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srisaravanavel srisaravanavel is offline

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Re: problem reading a in reverse order

Jul 26th, 2008

Print the entire file in reverse. not line by line.

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iamthwee

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Re: problem reading a in reverse order

Jul 26th, 2008

test.txt

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I am God yes I am
I know I am
dam right!

 Help with Code Tags 
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#include <iostream>
#include <string>
#include <fstream>
#include <vector>
#include <climits>
 
using namespace std;
 
class Foo
{
public:
  void reverse ( string t )
  {
    int s;
    s = t.length();
 
    for ( int i = s - 1; i >= 0; i-- )
    {
      cout << t[i];
    }
  }
};
 
int main()
{
  ifstream read ( "test.txt" );
  string line;
 
  vector <string> stuff;
 
  while ( getline ( read, line, '\n' ) )
  {
    stuff.push_back ( line );
  }
  read.close();
 
  int t;
  t = stuff.size();
 
  for ( int i = t - 1; i >= 0; i-- )
  {
    Foo test;
    test.reverse ( stuff[i] );
    cout << "\n";
  }
  cin.get();
}
#include <iostream>
#include <string>
#include <fstream>
#include <vector>
#include <climits>

using namespace std;

class Foo
{
public:
  void reverse ( string t )
  {
    int s;
    s = t.length();

    for ( int i = s - 1; i >= 0; i-- )
    {
      cout << t[i];
    }
  }
};

int main()
{
  ifstream read ( "test.txt" );
  string line;

  vector <string> stuff;

  while ( getline ( read, line, '\n' ) )
  {
    stuff.push_back ( line );
  }
  read.close();

  int t;
  t = stuff.size();

  for ( int i = t - 1; i >= 0; i-- )
  {
    Foo test;
    test.reverse ( stuff[i] );
    cout << "\n";
  }
  cin.get();
}

My output

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!thgir mad
ma I wonk I
ma I sey doG ma I

But I doubt that would work for you cos you're probably using turbo c 3.0 or something, in which case I would pretend you are writing a c program and use char arrays.

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Re: problem reading a in reverse order

Jul 26th, 2008

you can reverse using std::reverse :}
std::reverse(string.begin(), string.end());

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Re: problem reading a in reverse order

Jul 27th, 2008

> but goes to an infinite loop for a multiline file. Kindly suggest.
Because you only count bytes, not characters.

> ofile.seekg(-2,ios::cur);
By opening the file in text mode, you make it so "\r\n" is translated to "\n" when you read the file. So you get stuck in a "forward 2, back 2" loop.

For text files, it's best to read them line by line, then do whatever it is you need to do.

'seek'ing through text files is possible, but you can only seek to
- the beginning of the file
- the end of the file
- the result of a previous 'tell'