Re: dynamic array of ints

From: rossum (rossum48_at_coldmail.com)
Date: 07/30/04 

Date: Thu, 29 Jul 2004 23:44:16 +0100

On Wed, 28 Jul 2004 12:18:53 -0600, "John Hanley"
<jdhanley@telusplanet.net> wrote:

>I have an interesting problem and I'm not sure the best way to do this.
>
>I am reading in a variable number of integers from a file (eg. 001 002 003
>004 012 015). At compile time I have no idea how many will be there. But I
>need to parse them out and put them in an array.
>
>I could do an fscanf and just read until '\n', however I won't know how many
>are there and thus don't know how large to make my array.
>
>I could read it in as one large string, traverse through and count the
>number of ints and then allocate memory based on that. However I am not
>sure what to use to read the ints from the string. sscanf works but
>multiple calls to it start at the beginning of the string each time. And
>it seems like a sloppy way to do things anyway.
>
>Are there any suggestions as to what approach to take with this? I wanted
>to avoid using a link list as it seems like alot of work for maybe less than
>10 ints I need to parse out.
>
>Suggestions? Ideas?
>Thanks!
>
>
>
You don't say what language(s) you have available. This is a simple
task with a C++ vector.

// Reading a file of integers in C++

#include <vector>
#include <fstream>
#include <iostream>
#include <cstdlib>

main() {
    const char* INPUT_FILE_NAME = "file-of-integers.txt";

    // Open input file
    std::ifstream input_file;
    input_file.open(INPUT_FILE_NAME);
    if (!input_file) {
        std::cerr << "Could not open "
                  << INPUT_FILE_NAME
                  << " for reading\n";
        return EXIT_FAILURE;
    } // end if

    // Read integers into a vector
    std::vector<int> int_vec;
    int current_int = 0;
    while (input_file >> current_int) {
        int_vec.push_back(current_int);
    } // end while

    // Process integers in vector
    for (int i = 0; i < int_vec.size(); ++i) {
        if (i > 0) { std::cout << ", "; }
        std::cout << int_vec[i];
    } // end for
    std::cout << std::endl;

    return EXIT_SUCCESS;
} // end main()

-------------------------------

file-of-integers.txt
001 002 003 004 012 015 027

-------------------------------

program output:
1, 2, 3, 4, 12, 15, 27

-------------------------------

In order to keep things simple I have done no error checking on the
reading of the file. I don't know how reliable your input file is.

rossum 

--
The ultimate truth is that there is no Ultimate Truth

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