Dueling Generators - Advent of Code - 20171215

ac20171215.js

let generator = function(value, factor) {
  return (value * factor) % 2147483647;
};

let generatorA1 = function(value) {
  return generator(value, 16807);
};

let generatorA2 = function(value) {
  let found = false;
  while (!found) {
    value = generator(value, 16807)
    if (value % 4 == 0) {
      found = true;
    }
  }
  return value;
};

let generatorA = generatorA2;

let generatorB1 = function(value) {
  return generator(value, 48271);
};

let generatorB2 = function(value) {
  let found = false;
  while (!found) {
    value = generator(value, 48271)
    if (value % 8 == 0) {
      found = true;
    }
  }
  return value;
};

let generatorB = generatorB2;

let lower16Bits = function(number) {
  return number.toString(2).substr(-16);
};

let judge = function(size, seedA, seedB) {
  let valueA = generatorA(seedA);
  let valueB = generatorB(seedB);
  let count = 0;

  for (let i = 0; i <= size; i++) {
    let bitsA = lower16Bits(valueA);
    let bitsB = lower16Bits(valueB);
    if (bitsA == bitsB) {
      count++;
    }

    valueA = generatorA(valueA);
    valueB = generatorB(valueB);
  }

  return count;
};

let seedA = 883;
let seedB = 879;
let size = 5 * Math.pow(10, 6);
let result = judge(size, seedA, seedB);
console.log(result);