advent-code-2021-day-17.js

const assert = require("assert");

let xrange = [241, 273];
let yrange = [-97, -63];

function check([x, y], [vx, vy], maxHeight = 0, inShoot = false) {
  [x, y] = [x + vx, y + vy];

  // console.log([x, y], [vx, vy], maxHeight, inShoot);
  vx = vx > 0 ? vx - 1 : vx < 0 ? vx + 1 : 0;
  vy--;

  if (y > maxHeight) {
    maxHeight = y;
  }

  if (x >= xrange[0] && x <= xrange[1] && y >= yrange[0] && y <= yrange[1]) {
    inShoot = true;
  }

  // if x is beyond range and not finish
  if ((vx <= 0 && x < xrange[0]) || (vx >= 0 && x > xrange[1])) {
    return inShoot ? maxHeight : null;
  }

  if (vy < 0 && y < yrange[0]) {
    return inShoot ? maxHeight : null;
  }

  return check([x, y], [vx, vy], maxHeight, inShoot);
}

function run([vx, vy], expected) {
  const res = check([0, 0], [vx, vy]);
  console.log(res);
  assert(res === expected);
}

// run([17, -4], null);

// run([7, 2], 3);
// run([6, 3], 6);
// run([6, 9], 45);

let max = yrange[1];
let velocities = [];
for (let vx = 0; vx <= xrange[1]; vx++) {
  for (let vy = -1000; vy < 1000; vy++) {
    const h = check([0, 0], [vx, vy]);
    if (h != null) {
      max = Math.max(h, max);
      console.log([vx, vy], h);
      velocities.push([vx, vy]);
    }
  }
}

console.log(max, velocities.length);