C++ vector, what does this code mean?

Question

I have this code:

 const int maxnodes = 5000;
 struct Edge 
 {
   int to, rev;
   int f, cap;
 };

 vector g[maxnodes];

This is qui

Answer 1

This

int nodes = maxnodes, src, dest;

is a declaration that is equivalent to these three declarations

int nodes = maxnodes;
int src;
int dest;

This

vector g[maxnodes];

is a declaration of an array of objects of type std::vector. You can use the subscript operator with arrays.

So expression g[u] yields the element of the array with index u that is a reference to an object of type std::vector.

Class std::vector also overloads the subscript operator. So expression g[u][j] gives the object of type Edge with index j in the vector of the array with index u.

Dcelaration

Edge &e = g[u][j];

declares a reference to this object of type Edge.