Advent of Code 2021 - Day 05 A - TypeScript solution using mutable array

day05a.ts

function day05a(xs: [number, number, number, number][], matrix: number[][]) {
  xs.forEach((x) => {
    const [x1, y1, x2, y2] = x;

    if (x1 == x2 || y1 == y2) {
      for (let yi = Math.min(y1, y2); yi <= Math.max(y1, y2); yi++) {
        for (let xi = Math.min(x1, x2); xi <= Math.max(x1, x2); xi++)
          m[yi][xi]++;
      }
    }
  });

  return matrix
    .map((r) => r.map((x) => Number(x > 1)).reduce((a, b) => a + b, 0))
    .reduce((a, b) => a + b, 0);
}