let ty = [-171, -136];

​

// tx = [20, 30];

// ty = [-10, -5];

​

function setup() {

  createCanvas(1, 1);

  solve();

  noLoop();

}

​

// Part 1

// Since y vel is always -1 and vel is int

// and since y pos starts at 0, with any +ve initial

// y vel, the y pos MUST pass back to 0 with vel at -1 * initial vel - 1 (grav)

// Due to constraints on the target area, the lowest we can hit is at -171

// If we know we are passing through 0 again with (-1 * initial vel) - 1 

// and hitting the max of -171, then working backwards, the vel is -170 before 

// passing through 0 and there for 170 is initial vel;

​

​

function solve() {

  // part 1

  // maxYPos(170);

  let xrange = [0, tx[1]];

  let yrange = [ty[0], ty[0] * -1];

  let num = 0;

  for(let vx = xrange[0]; vx <= xrange[1]; vx ++) {

    for(let vy = yrange[0]; vy <= yrange[1]; vy ++) {

      // print(vx, vy);

      if(hits(vx, vy)) {

        // print("hit!");

        num ++;

      }

    }

  }

  print(num);

}

​

​

function hits(vx, vy) {

  let x = 0;

  let y = 0;

  while(!pastTarget(x, y)) {

    x += vx;

    y += vy;

    if(vx > 0) {

      vx -=1;

    }

    vy -= 1;

    if(inTarget(x, y)) {

      return true;

    }

  }

  return false;

}

​

function inTarget(x, y) {

  return x >= tx[0] && x <= tx[1] && y >= ty[0] && y <= ty[1];

}

​

function pastTarget(x, y) {

  return x > tx[1] || y < ty[0];

}

​

function maxYPos(vy) {

  let p = 0;

  while(vy >= 0) {

    p += vy;

    vy -= 1;

  }

  print(p);

}

​

​