Question

 #include <iostream>
 using namespace std;
 #include<stdlib.h>
 #include <cstdlib>
 #include <cmath>
 class Base
 {
   protected:
     int n;                                               // Allocate the dynamic memory.
     typedef double Coord[2];
     Coord* city_location;

     Base(int ncities) : n(ncities), city_location(new Coord[n]) {}
     ~Base() { delete [] city_location; }
 };



 template <class T> class Map;

 struct Flat;
 template <> class Map<Flat> : public Base
 {
   public:                                                   // Setting up the map in the flat euclidean version.

Map(int n) : Base(n)
{
  double Path[n];
  for (int i=0;i<n;i++)
  {
    city_location[i][0] = (static_cast <float> (rand()) / static_cast <float> (RAND_MAX))*80;
    city_location[i][1] = (static_cast <float> (rand()) / static_cast <float> (RAND_MAX))*80;
    Path[i] = i;
    cout << "city " << i << " is at (" << city_location[i][0] << "," << city_location[i][1] << ")\n";
  }

   cout << "\nThe initial path is (";

   for(int i=0;i<n;i++)
   {
        cout << Path[i]<< " ";
   }
    cout<< Path[0] <<")"<<endl;

//pathdistance(Path, n, distance());

}

double distance(int i, int j) const
{
  double dx = city_location[i][0] - city_location[j][0];
  double dy = city_location[i][1] - city_location[j][1];
  return sqrt(dx*dx+dy*dy);
}

一切正常，直到这一点，但我不知道如何将距离函数/ city_location传递给总距离函数。它以Path [n]定义的顺序成对计算点。

    double pathdistance(double Path,int n, double distance())     // Problem lies here, have tried with city_location and *city_location etc but can't figure it out.
{
    //cout<< city_location[0][1];
    double total = 0;
    for(int i=0; i<n-1;i++)
    {
       total += distance(Path[i],Path[i+1]);         \\Line 63

    }
        total += distance(Path[n],Path[0]);

        cout << "total distance is "<< total<<endl;
        return total;
     }

 };



 int main()
 {
   srand(1235);

   Map<Flat> x(10);
   // Map<Flat> x(10);

   cout << "distance between cities 3 and 7 is " << x.distance(3,7) << "\n";
 }

我收到以下错误：

 line 63: invalid types 'double[int]' for array subscript.

有关如何解决问题的任何想法？或者可能更简单的方法来解决我想要对总距离做些什么？感谢

Answer 1

您的path声明为double path，表示类型为double的单值，而不是数组。

对于传递数组，您可以将其作为double *path传递并通过索引访问元素或传递std::vector<double>（如果您的函数不更改向量元素，则为const引用）。

double pathDistance(double *Path, unsigned int n) // first one.

double pathDistance(const std::vector<double>& Path) // second alternative.

数组下标不正确

1 个答案: