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

1) int nodes = maxnodes, src, dest;

Here, nodes is an int initialized with the value same as that of maxnodes. src and dest are also int, but with no initial value.

2) vector g[maxnodes];

g is here an array of std::vector.

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

Q. What is g[u][j]?

A. It is the Edge stored in g at the uth row and jth column.

Q. g is vector filled with Edge struct, how can it be act like a array of arrays?

A. Because std::vector has operator[] overloaded for itself in its definition. Refer: http://en.cppreference.com/w/cpp/container/vector/operator_at