How to find all elements between two coordinates in a 2d array

Question

Essentially I'm trying to create the game reversi. To cut it short if you don't know what it is, I have a 8x8 board of squares. There are 2 coordinates and I need to determine all the squares that are between the two coordinates and fill them in. The 2 coordinates are either on the same y, same x or diagonal to each other.

Can someone explain the logic behind how I would go about doing something like this? How can I determine the coordinates of all the elements between the 2 coordinates.

Answer 1

You need a simple for loop, starting at one of the coordinates and moving towards the other.

let connect = (c1, c2) => {
  // Determine the distance between c1 & c2
  let delta = c1.map((v, i) => c2[i] - v);
  let distance = Math.max(...delta.map(v => Math.abs(v)));
  
  // Determine the unit vector (e.g. [1, -1]) to move each iteration
  let direction = delta.map(v => v / distance);
  
  // Starting at `c1`, iterate for `distance` iterations, moving in `direction` each iteration.
  return [...Array(distance + 1)].map((_, i) => c1.map((v, j) => v + direction[j] * i));
  
  // Same as above, but exclude `c1` and `c2` from the return array.
  // return [...Array(distance - 1)].map((_, i) => c1.map((v, j) => v + direction[j] * (i + 1)));
};

let c1 = [3, 6];
let c2 = [8, 1];
console.log(connect(c1, c2));