флойд

#include<iostream>
using namespace std;

const int INT = 10000000;
class Graph
{
  private:
  bool orient;
  int n, **arr, shet_reber, **d;

  public:
  Graph (int **matrix, int x, int shet)
  {
    n = x;
    arr = matrix;
    d = matrix;
    shet_reber = shet;
  }
  void minpath();
  int get_length_path(int x, int y);
};

void Graph::minpath()
{
  for (int l = 0; l < n; l++)
    for (int i = 0; i < n; i++)
      if (d[i][l] < INT)
        for (int j = 0; j < n; j++)
          d[i][j] = min(d[i][j], d[i][l] + d[l][j]);
}

int Graph::get_length_path(int x, int y)
{
 int dlina = 0;
  minpath();

 if (d[x][y] == INT)
  dlina = -1;
 else dlina = d[x][y];

 return dlina;
}

int main()
{
 int n, shet_reber = 0, x, y;
 cin >> n >> x >> y;

int **arr = new int*[n];

for ( int i = 0; i < n; i++)
     arr[i] = new int[n];

for (int i = 0; i < n; i++)
  for (int j = 0; j < n; j++)
     {
         cin >> arr[i][j];
         if (arr[i][j] == -1)
          arr[i][j] = INT;
         shet_reber++;
      }

 Graph object(arr, n, shet_reber);

 cout << object.get_length_path(x-1, y-1);
}