in C programming, how can we initialize this int *goo, where goo is a list of edges for a graph?

Question

In C programming, how can we initialize this int *goo, where goo is a list of edges for a graph?

Answer 1

A one-dimensional integer array cannot in general be used to store a graph intuitively, i.e. without some sort of mapping code.

There are at least two common ways to mathematically represent a graph in a matrix/array. Assuming N numbered vertices and M edges:

• An N x N adjacency matrix. This is a two-dimensional array, where each vertex has its own line.

• An M-sized adjacency list. This essentially boils down to a list of the edges and can be implemented as a M x 2 array, where each edge has its own line.

Both of these representations are intuitively two-dimensional K x L arrays. You can use a one-dimensional array by using extra code to place the data in a (K * L) x 1 one-dimensional array A. E.g. to get the (i, j) element of the original K x L array:

e = A[i * L + j];

Then you can simply allocate the array dynamically:

int *A = (int *)malloc(K * L * sizeof(int));

(Before anyone whines about the explicit cast, it is needed in C++ and that's a good enough reason for me)