Need help reading from a file until end of line

Question

I'm working on a a project for my class where I have to use all four algorithms for the maximum subarray sub problem (cubic, quadratic, linear, and recursive). My problem is that I'm supposed to read the input from a file and I'm having trouble figuring out how to read until the end of a line, execute code with that data, and then move onto the next line. The input file looks like this:

2
-5 -10 -2 -4
2
-2 10 -5 -6
3
-10 -5 0 5 -20 20 -50
4
10 8 2 -20 -50 -100 -150
0
-1 -2 -3 -4 -5
1
-100 -200 0
4
200 500 -700 1000 2000 -5000 4 10
4
100 200
6
0 0 0 0 0 0 -10
5
-4 10 -3 200 500 -700 2
0
5 10 15 20 25 30 35
2
10 30 50 70 100
3
-15 16 23 -30 0 -2 13 8 6 0 -4 -15
12
9 8 23 -1 -23 -4 0 0 4 7 9 10 -23 68 1 -2 -3 -6 -19 10 5 1 1 2 4 3 -46 12     -100 78 -23 0 0 12 2 7
5
-1 -3 0 2 3 6 1 -5 -3 -2

now my issue is that I want to be able to read in a single number (the minimum subarray length) and then fill the array with the row of numbers below it, then execute all four algorithms using that data, then I want to move on to the next minimum subarray length and the next array of values below it, execute all four algorithms etc., and I want to be able to do this all in one go.

For example, I want to read 2 as the minimum subarray length, then use (-5,-10,-2,-4) as the array, execute all four algorithms, then use 2 as the minimum length, (-5,10,-5,-6) as the array, execute all four algorithms, and keep doing that until the end of the file.

Zero effort to solve the problem shown by OP results in zero effort to solve the problem given by me. Sorry man. Here are some non-random keywords to get you started: `std::getline`, `std::stringstream`, `while (sstream >> number)` — user4581301, Oct 27 '15 at 01:23
use **getline** method to get whole lines at once and use **strtok** on alternate lines to split the line based on whitespaces — Swastik Padhi, Oct 27 '15 at 01:26
@CrakC `strtok` is a destructive function that does not work with std::string without copying the string to a char array, and using `std::getline` with anything other than std::string is a supremely ungood idea. — user4581301, Oct 27 '15 at 01:32

score 0 · Answer 1 · answered Oct 27 '15 at 01:40

Here is a quick possible solution that might help ("test.txt" contains your values...)

#include <fstream>
#include <iostream>
#include <sstream>
#include <vector>

using namespace std;

int main()
{
    ifstream in("test.txt");

    string str;
    int value;

    while (in)
    {
        vector<int> vec;

        getline(in, str);
        stringstream stream(str);

        while (stream)
        {
            stream >> value;
            vec.push_back(value);
        }
        vec.erase(vec.end()-1);

        //Here the vec conntains all values of the current line
        for (auto v : vec)
            cout << v << " ";
        cout << endl;
    }
}

Fails because `while (in)` tests for validity of the stream before making a read. [Variant of this.](http://stackoverflow.com/questions/5605125/why-is-iostreameof-inside-a-loop-condition-considered-wrong) Instead use `while (getline(in, str))` and `while (stream >> value)` in place of `while (stream)` — user4581301, Oct 27 '15 at 01:57

Need help reading from a file until end of line

1 Answers1