public static Complex GetCenter(Niku a, Niku b, Niku c)
{
var center = (a.Coordinate * a.Weight + b.Coordinate * b.Weight + c.Coordinate * c.Weight) / (a.Weight + b.Weight + c.Weight);
const double Eps = 1e-9;
const double Ratio = 0.8;
var nikus = new Niku[] { a, b, c };
Span <double> distances = stackalloc double[3];
while (true)
{
for (int i = 0; i < distances.Length; i++)
{
distances[i] = nikus[i].GetYakinikuTime(center);
}
var minIndex = -1;
var maxIndex = -1;
var min = double.MaxValue;
var max = double.MinValue;
for (int i = 0; i < distances.Length; i++)
{
if (min > distances[i])
{
min = distances[i];
minIndex = i;
}
if (max < distances[i])
{
max = distances[i];
maxIndex = i;
}
}
var second = 0.0;
for (int i = 0; i < distances.Length; i++)
{
if (i != minIndex && i != maxIndex)
{
second = distances[i];
}
}
if (max - second < Eps)
{
break;
}
else
{
var diff = (nikus[maxIndex].Coordinate - center) * (max - second) / max * Ratio;
center += diff;
}
}
return(center);
}
public override IEnumerable <object> Solve(TextReader inputStream)
{
var(nikuCount, toEat) = inputStream.ReadValue <int, int>();
var nikus = new Niku[nikuCount];
for (int i = 0; i < nikus.Length; i++)
{
var(x, y, c) = inputStream.ReadValue <int, int, int>();
nikus[i] = new Niku(new Complex(x, y), c);
}
double GetYakinikuTime(Complex fire)
{
var yakinikuTime = nikus.Select(niku => niku.GetYakinikuTime(fire)).OrderBy(t => t).Skip(toEat - 1).First();
return(yakinikuTime);
}
double minTime = double.MaxValue;
for (int i = 0; i < nikus.Length; i++)
{
var centerOne = nikus[i].Coordinate;
minTime = Math.Min(minTime, GetYakinikuTime(centerOne));
for (int j = i + 1; j < nikus.Length; j++)
{
var centerTwo = Niku.GetCenter(nikus[i], nikus[j]);
minTime = Math.Min(minTime, GetYakinikuTime(centerTwo));
for (int k = j + 1; k < nikus.Length; k++)
{
var centerThree = Niku.GetCenter(nikus[i], nikus[j], nikus[k]);
minTime = Math.Min(minTime, GetYakinikuTime(centerThree));
}
}
}
yield return(minTime);
}
public static Complex GetCenter(Niku a, Niku b) => (a.Coordinate * a.Weight + b.Coordinate * b.Weight) / (a.Weight + b.Weight);
