05.js

const opcode = op => {
  const str = String(op);
  return parseInt(str.substr(str.length - 2));
};

const mode = (op, pos) => {
  const str = String(op);
  if (pos + 2 > str.length) return 0;
  return parseInt(str.substr(str.length - (2 + pos), 1));
};

const param = (memory, pos, num) => {
  const op = memory[pos];
  const value = memory[pos + num];
  return mode(op, num) === 0 ? memory[value] : value;
};

const tick = (pos, memory, input, ram, debug = false) => {
  const op = opcode(memory[pos]);
  const p1 = param(memory, pos, 1);
  const p2 = param(memory, pos, 2);
  const p3 = param(memory, pos, 3);
  let to;
  switch (op) {
    case 1: // add
      to = memory[pos + 3];
      if (debug) console.log(`ADD: [${to}] = ${p1} + ${p2}`);
      memory[to] = p1 + p2;
      return pos + 4;
    case 2: // multiply
      to = memory[pos + 3];
      if (debug) console.log(`MUL: [${to}] = ${p1} * ${p2}`);
      memory[to] = p1 * p2;
      return pos + 4;
    case 3: // input
      to = memory[pos + 1];
      if (debug) console.log(`INP: [${to}] = ${input}`);
      memory[to] = input;
      return pos + 2;
    case 4: // output
      ram.output = p1;
      return pos + 2;
    case 5: // jump-if-true
      to = p2; //memory[pos + 2];
      if (debug) console.log(`IFT: ${p1} !== 0 => ${p1 !== 0}`);
      if (p1 !== 0) {
        if (debug) console.log(`JMP: [${to}]`);
        return to;
      }
      return pos + 3;
    case 6: // jump-if-false
      to = p2; //memory[pos + 2];
      if (debug) console.log(`IFT: ${p1} === 0 => ${p1 === 0}`);
      if (p1 === 0) {
        if (debug) console.log(`JMP: [${to}]`);
        return to;
      }
      return pos + 3;
    case 7: // less than
      to = memory[pos + 3];
      if (debug) {
        console.log(`ILT: ${p1} < ${p2} => ${p1 < p2}`);
        console.log(`[${to}] = ${p1 < p2 ? 1 : 0}`);
      }
      memory[to] = p1 < p2 ? 1 : 0;
      return pos + 4;
    case 8: // equals
      to = memory[pos + 3];
      if (debug) {
        console.log(`IEQ ${p1} === ${p2} => ${p1 === p2}`);
        console.log(`[${to}] = ${p1 === p2 ? 1 : 0}`);
      }
      memory[to] = p1 === p2 ? 1 : 0;
      return pos + 4;
    case 99: // halt
      if (debug) console.log("HLT");
      return -1;
    default:
      console.log(`unknown opcode ${op}`);
      return -1;
  }
};

const run = (program, input, debug = false) => {
  const ram = {};
  const memory = program.split(",").map(str => parseInt(str, 10));
  let pos = 0;
  while (pos > -1) pos = tick(pos, memory, input, ram, debug);
  return ram.output;
};

const tests = [
  {
    name:
      "Using position mode, consider whether the input is equal to 8; output 1 (if it is) or 0 (if it is not).",
    program: "3,9,8,9,10,9,4,9,99,-1,8",
    cases: [
      { input: 8, output: 1 },
      { input: 9, output: 0 }
    ]
  },
  {
    name:
      "Using position mode, consider whether the input is less than 8; output 1 (if it is) or 0 (if it is not).",
    program: "3,9,7,9,10,9,4,9,99,-1,8",
    cases: [
      { input: 7, output: 1 },
      { input: 8, output: 0 }
    ]
  },
  {
    name:
      "Using immediate mode, consider whether the input is equal to 8; output 1 (if it is) or 0 (if it is not).",
    program: "3,3,1108,-1,8,3,4,3,99",
    cases: [
      { input: 8, output: 1 },
      { input: 9, output: 0 }
    ]
  },
  {
    name:
      "Using immediate mode, consider whether the input is less than 8; output 1 (if it is) or 0 (if it is not).",
    program: "3,3,1107,-1,8,3,4,3,99",
    cases: [
      { input: 7, output: 1 },
      { input: 8, output: 0 }
    ]
  },
  {
    name:
      "Using position mode, take an input, then output 0 if the input was zero or 1 if the input was non-zero.",
    program: "3,12,6,12,15,1,13,14,13,4,13,99,-1,0,1,9",
    cases: [
      { input: 0, output: 0 },
      { input: 2, output: 1 }
    ]
  },
  {
    name:
      "Using immediate mode, take an input, then output 0 if the input was zero or 1 if the input was non-zero.",
    program: "3,12,6,12,15,1,13,14,13,4,13,99,-1,0,1,9",
    cases: [
      { input: 0, output: 0 },
      { input: 2, output: 1 }
    ]
  },
  {
    name:
      "Outputs 999 if the input value is below 8, output 1000 if the input value is equal to 8, or output 1001 if the input value is greater than 8.",
    program:
      "3,21,1008,21,8,20,1005,20,22,107,8,21,20,1006,20,31,1106,0,36,98,0,0,1002,21,125,20,4,20,1105,1,46,104,999,1105,1,46,1101,1000,1,20,4,20,1105,1,46,98,99",
    cases: [
      { input: 4, output: 999 },
      { input: 8, output: 1000 },
      { input: 10, output: 1001 }
    ]
  }
];

tests.forEach(test => {
  let pass = true;
  test.cases.forEach(({ input, output }) => {
    const actual = run(test.program, input);
    if (actual !== output) {
      pass = false;
      console.log("Fail: " + test.name);
      console.log(`Output was ${actual} should be ${output}`);
    }
  });
  console.log("Pass: " + test.name);
});

const program = require("fs")
  .readFileSync("./05.txt")
  .toString();

console.log(run(program, 1));
console.log(run(program, 5));