Submission #23374649

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Source Code Expand

import std.stdio, std.algorithm, std.conv, std.string, std.array, std.math;

double epsilon = 0.0000001;

double lostval(double[] a, double x)
{
  return a.fold!((acc, v) => acc + v + x - min(v, 2.0 * x))(0.0) / a.length;
}

double d_lostval(double[] a, double x)
{
  return a.fold!((acc, v) => acc - (v - 2.0 * x) / abs(v - 2.0 * x))(0.0);
}

double solve(double[] a, double bad, double good)
{
  int count = 100;

  while (count--) {
    double mid = (bad + good) / 2;
    double d = d_lostval(a, mid);
    while (d.isNaN) {
      mid += epsilon;
      d = d_lostval(a, mid);
    }
    if (d < 0)
      bad = mid;
    else
      good = mid;
  }
  return good;
}

void main()
{
  int n;
  readf!" %d "(n);
  auto a = readln.strip.split.map!(to!double).array;
  double min_x = 0.0;
  double max_x = a.maxElement;

  double x = solve(a, min_x, max_x);
  writefln("%.18f", lostval(a, x));
}

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