a. read the lines and insert it into a vector

C++ Syntax (Toggle Plain Text)

ifstream file("customer.txt") ;
string rec ;
vector<string> records ;
while( getline(file,rec) ) 
    records.push_back(rec) ;

ifstream file("customer.txt") ; string rec ; vector<string> records ; while( getline(file,rec) ) records.push_back(rec) ;

b. iterate over the vector backwards to
access the redords in reverse order

C++ Syntax (Toggle Plain Text)

  ofstream outfile("custFileCopy.txt") ;
  std::copy( records.rbegin(), records.rend(),
        std::ostream_iterator<string>(outfile) );

ofstream outfile("custFileCopy.txt") ; std::copy( records.rbegin(), records.rend(), std::ostream_iterator<string>(outfile) );

you can do this only if the file is small enough;
for very large files memory may not be sufficient.
u could however read the file in parts (say 1000 records),
create intermediate output files (as above) and then
merge them in reverse order of creation.

*** note: i had not seen Lerner's post; it came in while i was
typing in the reply. so this is just a repetition of what was
suggested in that post

to fix the compiler error:
u need to declare the function before u
call it. add the following anywhere before
the call.

C++ Syntax (Toggle Plain Text)

void backward(vector <int> vect) ;

void backward(vector <int> vect) ;

a vector is really a dynamically resizeable
array; paasing it by value is not a good
idea at all.
(u are copying a large collection!)
in general, for any user defined type,
prefer passing by const referance instead
of by value. so i would also suggest u
change the signature of backward to

C++ Syntax (Toggle Plain Text)

void backward( const vector<int>& vect ) ;

void backward( const vector<int>& vect ) ;

were u not trying to read strings (lines)
from the file (not integers) in the original
post?

IMO, sometime STL classes are more hassle than they are worth. One such occassion is during a class when the instructions are to use an array. Another is when the upper bounds of the array are given. And another is when the user has no idea what a template or an iterator is.

C++ Syntax (Toggle Plain Text)

ifstream fin("inputFile.txt"); //to read from file
ofstream fout("outputFile.txt"); //to write back to file 
string input[100]; //to hold input
int i = 0;  //to keep track of how many strings actually read in, may be less than max possible.
 
//validate files are open here
 
//read input file one string at a time, adding it to the array in the appropriate index
while(getline(fin, input[i]))
   i++;
 
//write to output file (frontwards for this demonstration) one string per line
for(int x  = 0; x < i; ++x)
      fout << input[i] << endl;
 
//close files here

ifstream fin("inputFile.txt"); //to read from file ofstream fout("outputFile.txt"); //to write back to file string input[100]; //to hold input int i = 0; //to keep track of how many strings actually read in, may be less than max possible. //validate files are open here //read input file one string at a time, adding it to the array in the appropriate index while(getline(fin, input[i])) i++; //write to output file (frontwards for this demonstration) one string per line for(int x = 0; x < i; ++x) fout << input[i] << endl; //close files here

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