Loading array from file - c++

Question

I'm trying to load a file of integers, add them to a 2D array, iterate through the array, and add tiles to my level based on the integer(Tile ID)at the current index. My problem seems to be that the array is loaded/iterated through in the wrong order. This is the file I'm loading from:
test.txt
02 02 02 02 02 02 02 02 02 02 02 02 02 02 02
01 01 01 01 01 01 01 01 01 01 01 01 01 01 01
01 01 01 01 01 01 01 01 01 01 01 01 01 01 01
01 01 01 01 01 01 01 01 01 01 01 01 01 01 01
01 01 01 01 01 01 01 01 01 01 01 01 01 01 01
01 01 01 01 01 01 01 01 01 01 01 01 01 01 01
01 01 01 01 01 01 01 01 01 01 01 01 01 01 01
01 01 01 01 01 01 01 01 01 01 01 01 01 01 01
01 01 01 01 01 01 01 01 01 01 01 01 01 01 01
This is the level constructor:
Level::Level(std::string levelpath, int _width, int _height)
{
std::ifstream levelfile(levelpath);
width = _width;
height = _height;
int ids[15][9];
while (levelfile.is_open()) {
std::copy_n(std::istream_iterator<int>(levelfile), width * height, &ids[0][0]);
for (int y = 0; y < height; ++y) {
for (int x = 0; x < width; ++x) {
tiles.push_back(getTile(ids[x][y], sf::Vector2f(x * Tile::SIZE, y * Tile::SIZE)));
std::cout << ids[x][y] << " ";
}
std::cout << std::endl;
}
levelfile.close();
}
}
And this is how I create the level:
level = std::unique_ptr<Level>(new Level("data/maps/test.txt", 15, 9));
Here's the output in the console:
2 2 1 1 1 1 1 1 1 1 1 1 1 1 1
2 2 1 1 1 1 1 1 1 1 1 1 1 1 1
2 2 1 1 1 1 1 1 1 1 1 1 1 1 1
2 2 1 1 1 1 1 1 1 1 1 1 1 1 1
2 2 1 1 1 1 1 1 1 1 1 1 1 1 1
2 2 1 1 1 1 1 1 1 1 1 1 1 1 1
2 1 1 1 1 1 1 1 1 1 1 1 1 1 1
2 1 1 1 1 1 1 1 1 1 1 1 1 1 1
2 1 1 1 1 1 1 1 1 1 1 1 1 1 1
As you can see the contents are the same as in test.txt, but in the wrong order.

Answer 1

The reason is that you swapped the dimensions of the array. Instead of
int ids[15][9];
...which is 15 lines of 9 elements, you want
int ids[9][15];
...which is 9 lines of 15 elements. The order of the extents in the declaration is the same as the order of indices in access.
EDIT: ...which you also swapped. Instead of
ids[x][y]
you need
ids[y][x]
That does rather better explain the output you get, come to think of it. 2D-Arrays in C++ are stored row-major, meaning that the innermost arrays (the ones stored contiguously) are the ones with the rightmost index. Put another way, ids[y][x] is stored directly before ids[y][x + 1], whereas there is some space between ids[y][x] and ids[y + 1][x].
If you read in a row-major array like you do with std::copy_n and interpret it as a column-major array, you get the transpose (a bit warped because of the changed dimensions, but recognizably so. If you swapped height and width, you'd see the real transpose).

Answer 2

int ids[9][15];
while (levelfile.is_open()) {
std::copy_n(std::istream_iterator<int>(levelfile), width * height, &ids[0][0]);
for (int y = 0; y < height; ++y) {
for (int x = 0; x < width; ++x) {
tiles.push_back(getTile(ids[y][x], sf::Vector2f(x * Tile::SIZE, y * Tile::SIZE)));
std::cout << ids[y][x] << " ";
}
std::cout << std::endl;
}

Answer 3

If you look you can see that your print the first 15 values (the need to be in the first line) in the first raw (and what doesn't fit in the second). You can understand that it start filling the rows before the lines and your file contain first the line. So load your map "on the side". Set the height as the width (15) and the opposite (the width is 9 and not 15). Now you will load the map correctly.
Not just print each row and "endl" before the second row (each row print as line). And you will see this ok.
Hope it was clear enough.