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Have a number correspond to a position in a multi dimensional array (map 1D numeric values to 2D)

July 1, 2022

I would like the user to input a number 1-9 and have that number correspond to a position on a 3×3 2d array. And then change the value in that array to an "x".

int input = Convert.ToInt32(Console.ReadLine());

string[,] numbers = { 
                    { " ", " ", " " },
                    { " ", " ", " " }, 
                    { " ", " ", " " }
                    };

At first I decided to do this:

int x = input % 3 - 1;
int y = input / 3 - 1;

And then access the array at numbers[y, x] however this caused problems with the index being out of bounds.

>Solution :

You had a somewhat good intuition for subtracting 1, but you did it in a wrong way.

The correct would be:

int x = (input-1) % 3;
int y = (input-1) / 3;

Subtracting 1 from the input (in the range 1..9) will translate it to the range 0..8.
Then using / and % with 3, will get you the x,y coordinates, both in 0..2 range.