Advent of Code 2019

index.re

// # Day 1
[@bs.val] external document: Js.t({..}) = "document";

let container = document##createElement("div");
let () = document##body##appendChild(container);

ReactDOMRe.render(<RocketFuelCalculator />, container);

// # Day 2

let solveIntCodeProgram = final => {
  let rec solver = (a, b) =>
    if (!(a > 99 && b > 99)) {
      let result = IntCode.runProgram(IntCode.createProgram(a, b));
      if (result === final) {
        [a, b];
      } else if (a === 99) {
        solver(0, b + 1);
      } else {
        solver(a + 1, b);
      };
    } else {
      [0, 0];
    };
  solver(0, 0);
};

Js.log(solveIntCodeProgram(19690720));

IntCode.re

let template = [
  3,
  1,
  1,
  2,
  3,
  1,
  3,
  4,
  3,
  1,
  5,
  0,
  3,
  2,
  13,
  1,
  19,
  1,
  6,
  19,
  23,
  2,
  6,
  23,
  27,
  1,
  5,
  27,
  31,
  2,
  31,
  9,
  35,
  1,
  35,
  5,
  39,
  1,
  39,
  5,
  43,
  1,
  43,
  10,
  47,
  2,
  6,
  47,
  51,
  1,
  51,
  5,
  55,
  2,
  55,
  6,
  59,
  1,
  5,
  59,
  63,
  2,
  63,
  6,
  67,
  1,
  5,
  67,
  71,
  1,
  71,
  6,
  75,
  2,
  75,
  10,
  79,
  1,
  79,
  5,
  83,
  2,
  83,
  6,
  87,
  1,
  87,
  5,
  91,
  2,
  9,
  91,
  95,
  1,
  95,
  6,
  99,
  2,
  9,
  99,
  103,
  2,
  9,
  103,
  107,
  1,
  5,
  107,
  111,
  1,
  111,
  5,
  115,
  1,
  115,
  13,
  119,
  1,
  13,
  119,
  123,
  2,
  6,
  123,
  127,
  1,
  5,
  127,
  131,
  1,
  9,
  131,
  135,
  1,
  135,
  9,
  139,
  2,
  139,
  6,
  143,
  1,
  143,
  5,
  147,
  2,
  147,
  6,
  151,
  1,
  5,
  151,
  155,
  2,
  6,
  155,
  159,
  1,
  159,
  2,
  163,
  1,
  9,
  163,
  0,
  99,
  2,
  0,
  14,
  0,
];

let createProgram = (a, b) => {
  [1, a, b, ...template];
};

let execute = (program, memory) => {
  switch (program) {
  | [1, a, b, pointer, ...rest] =>
    // add a to b, save to pointer
    memory[pointer] = memory[a] + memory[b];
    rest;
  | [2, a, b, pointer, ...rest] =>
    // multiply a with b, save to pointer
    memory[pointer] = memory[a] * memory[b];
    rest;
  | [3, pointer, ...rest] =>
    // Example of extra instruction, increase value at pointer
    memory[pointer] = memory[pointer] + 1;
    rest;
  | [_, ...rest] => rest
  | [] => []
  };
};

let rec compute = (program, memory) => {
  let restProgram = execute(program, memory);

  let isDone =
    switch (restProgram) {
    | [99, ..._] => true // if the program is at the end tag
    | [] => true // or if there is nothing left
    | _ => false
    };

  if (!isDone) {
    compute(restProgram, memory);
  };
};

let runProgram = program => {
  let memory = Array.of_list(program);
  compute(program, memory);
  memory[0];
};

RocketFuelCalculator.re

let minFuel = 6.0;
let rec calculateFuel = mass => {
  let fuel = floor(mass /. 3.0) -. 2.0;
  fuel > minFuel ? fuel +. calculateFuel(fuel) : fuel;
};

[@react.component]
let make = () => {
  let (input, setInput) = React.useState(() => "");

  let style =
    ReactDOMRe.Style.make(
      ~background="#eee",
      ~maxWidth="1200px",
      ~margin="0 auto",
      (),
    );

  let ships = Js_string.split("\n", input);
  let totalFuel =
    Belt.Array.reduce(ships, 0.0, (i, j) =>
      switch (j) {
      | "" => i
      | _ =>
        let shipMass =
          try (float_of_string(j)) {
          | Failure(_) => minFuel
          };
        i +. calculateFuel(shipMass);
      }
    );

  let shipsCounter =
    React.string("Ships: " ++ string_of_int(Array.length(ships)));

  let fuelString =
    React.string("Total fuel: " ++ Js.Float.toString(totalFuel));

  <div style>
    <br />
    <textarea
      name="mass"
      onChange={_e => {
        let input = _e->ReactEvent.Form.target##value;
        setInput(_ => input);
      }}
    />
    <hr />
    <strong> fuelString </strong>
    <br />
    <em> shipsCounter </em>
  </div>;
};