Particle Swarm - Advent of Code - 20171220

ac20171220.js

let particles = require('./particles');

let stepParticles = function(particles) {
  return particles.map(p => {
      p.v = p.v.map((c, i) => c + p.a[i]);
      p.p = p.p.map((c, i) => c + p.v[i]);
    return p;
  });
};

let moveParticles_1 = function(particles) {
  let positions;
  for (let i = 0; i < 1000; i++) {
    particles = stepParticles(particles);
  }

  return particles;
};

// Move Particles with collision detection
let moveParticles_2 = function(particles) {
  let positions;
  for (let i = 0; i < 1000; i++) {
    particles = stepParticles(particles);

    positions = particles.reduce((acc, p, i) => {
        let location = p.p.join(',');
        if (acc.hasOwnProperty(location)) {
          acc[location].push(i);
        } else {
          acc[location] = [i];
        }
      return acc;
    }, {});

    Object.values(positions).forEach(location => {
      if (location.length > 1) {
        location.forEach(i => {
          particles[i] = false;
        });
      }
    });

    particles = particles.filter(p => p);
  }

  return particles;
};

let moveParticles = moveParticles_2;

let findNearestParticle = function(particles) {
  particles = moveParticles(particles);
  particles = particles.map(
    p => Math.abs(p.p[0]) + Math.abs(p.p[1]) + Math.abs(p.p[2])
  );
  let closest = Math.min(...particles);
  return [particles.indexOf(closest), particles.filter(p => p).length];
};

let result;
result = findNearestParticle(particles);
console.log(result);