dimi-math.js

// Cubic equation calculator sourced from StackOverflow
const {spawn} = require('child_process');
let nc = spawn('nc', ['ctf.dimigo.hs.kr', 8231]);
nc.stdout.on('data', (data) => {
  console.log(data.toString());
  if (data.toString().replace(/\n/g, '').startsWith('No. ')) {
    const matches = data.toString().match(/([0-9]+)x\^3 ([\+-]) ([0-9]+)x\^2 ([\+-]) ([0-9]+)x ([\+-]) ([0-9]+) = 0/);
    let solved = solveCubic(...([matches[1], matches[2] + matches[3], matches[4] + matches[5], matches[6] + matches[7]].map(num => Number(num)))).map(num => Math.round(num));
    if (solved.length === 1) {
      console.log('Enter manually');
      return;
    }
    if (solved.length === 2) {
      solved[2] = solved[0];
    }
    solved = solved.join(', ');
    nc.stdin.write(`${solved}\n`);
  }
});
nc.on('close', () => process.exit());
process.stdin.pipe(nc.stdin);

function cuberoot(x) {
    var y = Math.pow(Math.abs(x), 1/3);
    return x < 0 ? -y : y;
}

function solveCubic(a, b, c, d) {
    if (Math.abs(a) < 1e-8) {
        a = b; b = c; c = d;
        if (Math.abs(a) < 1e-8) {
            a = b; b = c;
            if (Math.abs(a) < 1e-8)
                return [];
            return [-b/a];
        }

        var D = b * b - 4 * a * c;
        if (Math.abs(D) < 1e-8)
            return [-b/(2*a)];
        else if (D > 0)
            return [(-b+Math.sqrt(D))/(2*a), (-b-Math.sqrt(D))/(2*a)];
        return [];
    }

    var p = (3*a*c - b*b)/(3*a*a);
    var q = (2*b*b*b - 9*a*b*c + 27*a*a*d)/(27*a*a*a);
    var roots;

    if (Math.abs(p) < 1e-8) {
        roots = [cuberoot(-q)];
    } else if (Math.abs(q) < 1e-8) {
        roots = [0].concat(p < 0 ? [Math.sqrt(-p), -Math.sqrt(-p)] : []);
    } else {
        var D = q*q/4 + p*p*p/27;
        if (Math.abs(D) < 1e-8) {
            roots = [-1.5*q/p, 3*q/p];
        } else if (D > 0) {
            var u = cuberoot(-q/2 - Math.sqrt(D));
            roots = [u - p/(3*u)];
        } else {
            var u = 2*Math.sqrt(-p/3);
            var t = Math.acos(3*q/p/u)/3;
            var k = 2*Math.PI/3;
            roots = [u*Math.cos(t), u*Math.cos(t-k), u*Math.cos(t-2*k)];
        }
    }

    for (var i = 0; i < roots.length; i++)
        roots[i] -= b/(3*a);

    return roots;
}