Text data to an array

[The Midnighter]

I'm trying to create a maze solver here, I've got my text file loaded and it looks fine - I just need to figure out how to make it a 2D array... Here's all I have so far:

#include <iostream>
#include <fstream>
#include <string>
#include <vector>
using namespace std;
 
int main (int argc, char* argv[])
{
    vector<string> text_file;
    string line;
    ifstream myFile (argv[1]);
    int N;
 
    if (myFile.is_open())
    {
        while (getline(myFile,line))
            text_file.push_back(line);
        N = (text_file.size()-1)/2; 
 
    }
    else
    {
        cout << "Unable to open file: " << argv[1] << "\n";
    }
 
    return 0;
}

[weaknessforcats]

It already is a 2D array.

Read this:

First, there are only one-dimensional arrays in C or C++. The number of elements in put between brackets:

int array[5];
 

That is an array of 5 elements each of which is an int.

int array[];
 

won't compile. You need to declare the number of elements.

Second, this array:

int array[5][10];
 

is still an array of 5 elements. Each element is an array of 10 int.

int array[5][10][15];
 

is still an array of 5 elements. Each element is an array of 10 elements where each element is an array of 15 int.

int array[][10];
 

won't compile. You need to declare the number of elements.

Third, the name of an array is the address of element 0

int array[5];
 

Here array is the address of array[0]. Since array[0] is an int, array is the address of an int. You can assign the name array to an int*.

int array[5][10];
 

Here array is the address of array[0]. Since array[0] is an array of 10 int, array is the address of an array of 10 int. You can assign the name array to a pointer to an array of 10 int:

int array[5][10];
 
int (*ptr)[10] = array;
 

Fourth, when the number of elements is not known at compile time, you create the array dynamically:

int* array = new int[value];
int (*ptr)[10] = new int[value][10];
int (*ptr)[10][15] = new int[value][10][15];
 

In each case value is the number of elements. Any other brackets only describe the elements.

Using an int** for an array of arrays is incorrect and produces wrong answers using pointer arithmetic. The compiler knows this so it won't compile this code:

int** ptr = new int[value][10];    //ERROR
 

new returns the address of an array of 10 int and that isn't the same as an int**.

Likewise:

int*** ptr = new int[value][10][15];    //ERROR
 

new returns the address of an array of 10 elements where each element is an array of 15 int and that isn't the same as an int***.

With the above in mind this array:

int array[10] = {0,1,2,3,4,5,6,7,8,9};
 

has a memory layout of

0 1 2 3 4 5 6 7 8 9

Wheras this array:

int array[5][2] = {0,1,2,3,4,5,6,7,8,9};
 

has a memory layout of

0 1 2 3 4 5 6 7 8 9

Kinda the same, right?

So if your disc file contains

0 1 2 3 4 5 6 7 8 9

Does it make a difference wheher you read into a one-dimensional array or a two-dimensional array? No.

Therefore, when you do your read use the address of array[0][0] and read as though you have a
one-dimensional array and the values will be in the correct locations.

Based on the above your vector<string> can be used as a 2D array, say a
[4][3] just based on how you manipulate the array.

Let's say you want the string [2][1].

That would be 2 * 3 for the row and1 for the column.

That is, 2 * 3 + 1 = 7

Use [7] of your vector.

This is the same calculation the compiler uses to navigate an array that wishes to be used as 2D.