Storing data into a multidimensional array

Question

I could use some help. I am trying to read from a file. the file contains this:

1x+1y+1z=5
2x+3y+5z=8
4x+0y+5z=2

I want to store this into a two dimensional array. Rows are 3 and columns will always be 4. I only want to store the integer values, in this case that will be 1 1 1 5 2 3 5 8 4 0 5 2. How can I store this values into the array? This is what I tried to doing but it is not working. Thank you for the help.

int main(){

    fstream file;


    file.open("matrix.txt", ios::in);



    int arr[3][4];


        // copy integers into array and display
        for (int i = 0; i < 3; i++){
            for(int j= 0; j < 4; j++){
            file >> arr[i][j];
            cout << arr[i][j];
            }
        }




}

This question needs clarification. If each line corresponds to a player, why ask the user for the number of players ? How is it that you're extracting just the numbers from the input file ? I see no parsing / tokenizing ? — user501138
– user501138, Commented Oct 2, 2017 at 2:59
@user501138, no need to know the number of players. What I want to know is if there is any way I can store the equation into an array where I can manipulate the numbers using pointers? — Dany
– Dany, Commented Oct 2, 2017 at 3:04
Why are you issuing a delete [] arr when arr is not dynamically allocated using new[]? Also, this has more to do with trying to convert the string "1x+1y+1z=5" and strings looking like this into an array with 4 elements. This has virtually nothing to do with file reading. — PaulMcKenzie
– PaulMcKenzie, Commented Oct 2, 2017 at 3:07

CroCo · Accepted Answer · 2017-10-02 03:48:36Z

You need first to extract numbers from each equation and then store them in the array. I will show you how to extract these numbers and the rest is trivial I guess.

#include <iostream>
#include <string>
using namespace std;


void getNumbers(string str, int&x, int&y, int& z)
{
    string X, Y, Z;

    size_t idx = str.find("x");
    size_t idy = str.find("y");
    size_t idz = str.find("z");

    X = str.substr(0, idx);
    Y = str.substr(idx+1, idy-(idx+1));
    Z = str.substr(idy+1, idz-(idy+1));

    x = stoi(X);
    y = stoi(Y);
    z = stoi(Z);
}

int main()
{
    string line("2x+82y-12z=5");

    int x(0), y(0), z(0);
    getNumbers(line,x,y,z);
    cout << line << endl;
    cout << x << "  " << y << "  " << z << endl;
    return 0;
}

The result is

2x+82y-12z=5
2  82  -12

Cedrick Clemente · Accepted Answer · 2017-10-02 03:16:09Z

1

if i am in your position, i will first tokenize every line you get in the file and slice up every number. then i will store it in the array (dont forget to cast every number to integer.)

answered Oct 2, 2017 at 3:16

Cedrick Clemente

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