C++ Bc. 10 cpp

#include <iostream>
#include <string>
#include <algorithm>
#include <matvec/matvec.h>

struct Chyba
{
  template <typename T> Chyba(T t) : text(t) {}

  std::string text;
};


double determinant(GNU_gama::Mat<>& A)
{
  // matice musi byt ctvercova a nesmi mit nulovy rozmer
  const int N = A.rows();
  if (N != A.cols() || N == 0) throw Chyba("chybny rozmer matice");

  // D registruje zmeny znamenka determinantu
  double D = 1;

  // hlavni cyklus anuluje prvky pod hlavni diagonalou
  for (int k=1; k<N; k++)
    {
      // vyber pivotniho prvku
      double pivot = std::abs(A(k,k));
      int    index = k;
      for (int i=k+1; i<=N; i++)
        if (std::abs(A(i,k)) > pivot)
          {
            pivot = std::abs(A(i,k));
            index = i;
          }
      
      // nulovy prvek na diagonale znamena, ze matice neni regularni
      if (pivot == 0) return 0;


      // vymena pivotniho radku znamena zmenu znamenka determinantu
      if (index != k)
        {
          D *= -1;
          for (int j=k; j<=N; j++)
            std::swap(A(index,j), A(k,j));
        }

      // vynulovani sloupce pod pivotnim prvkem
      for (int i=k+1; i<=N; i++)
        {
          double p = A(i,k)/A(k,k);
          A(i,k) = 0;
          for (int j=k+1; j<=N; j++) 
            A(i,j) -= p*A(k,j);
        }
    }

  // soucin prvku na hlavni diagonale
  double S = 1;
  for (int k=1; k<=N; k++) S *= A(k,k);

  return D*S;
}


int main()
{
  try 
    {
      GNU_gama::Mat<> A(4,4);   // det(A) je 12
      A = 
        0,  2,  2,  4,
        1,  2,  3,  4,
        3,  0,  9,  8,
        2,  7,  0,  1;
      
      std::cout << "det(A) = " << determinant(A) << "\n"; 

      GNU_gama::Mat<> B(9,9);   // det(B) je 1
      B = 
        4917, 5081, 5242, 5397, 5542, 5672, 5781, 5862, 5907,
        5081, 5253, 5421, 5582, 5732, 5866, 5978, 6061, 6107,
        5242, 5421, 5596, 5763, 5918, 6056, 6171, 6256, 6303,
        5397, 5582, 5763, 5936, 6096, 6238, 6356, 6443, 6491,
        5542, 5732, 5918, 6096, 6261, 6407, 6528, 6617, 6666,
        5672, 5866, 6056, 6238, 6407, 6557, 6681, 6772, 6822,
        5781, 5978, 6171, 6356, 6528, 6681, 6808, 6901, 6952,
        5862, 6061, 6256, 6443, 6617, 6772, 6901, 6996, 7048,
        5907, 6107, 6303, 6491, 6666, 6822, 6952, 7048, 7101;

      std::cout << "det(B) = " << determinant(B) << "\n"; 
    }
  catch(Chyba& ch)
    {
      std::cout << "Chyba : " << ch.text << "\n";
    }
}

[ Zpět ]