Cod sursa(job #1968225)

Utilizator TincaMateiTinca Matei TincaMatei Data 17 aprilie 2017 15:50:56
Problema Adapost 2 Scor 80
Compilator cpp Status done
Runda Arhiva de probleme Marime 1.02 kb
#include <cstdio>
#include <cmath>
//retard trying to learn gradient descent
typedef double f64;
const int MAX_N = 50000;
const f64 EPS = 1e-5f;
f64 x[MAX_N], y[MAX_N];

inline f64 calc(f64 xP, f64 yP, int n) {
  f64 s = 0.0f;
  for(int i = 0; i < n; ++i)
    s = s + sqrt((xP - x[i]) * (xP - x[i]) + (yP - y[i]) * (yP - y[i]));
  return s;
}

int main() {
  int n;
  FILE *fin = fopen("adapost2.in", "r");
  fscanf(fin, "%d", &n);
  for(int i = 0; i < n; ++i)
    fscanf(fin, "%lf%lf", &x[i], &y[i]);

  fclose(fin);

  f64 pas = 250.0f;
  f64 x = 500.0f;
  f64 y = 500.0f;
  f64 xdelta, ydelta;
  do {
    xdelta = (calc(x + EPS, y, n) - calc(x, y, n)) / EPS;
    ydelta = (calc(x, y + EPS, n) - calc(x, y, n)) / EPS;
    if(xdelta < 0.0f)
      x = x + pas;
    else
      x = x - pas;

    if(ydelta < 0.0f)
      y = y + pas;
    else
      y = y - pas;
    pas = pas * 2.0f / 3.0f;
  } while(fabs(xdelta) > EPS || fabs(ydelta) > EPS);

  FILE *fout = fopen("adapost2.out", "w");
  fprintf(fout, "%f %f", x, y);
  fclose(fout);
  return 0;
}