define a function insertEdge(u, v, w, g) that adds an edge between u and v of weight w to graph g. If the edge array is full, insertEdge must refuse to add the edge.

Here is a suitable contract for insertEdge. Note its similarity to the preceding paragraph.

 // insertEdge(u, v, w, g) inserts an edge of weight w between vertices // u and v into graph g. // // If there is not enough room in g to add the edge, then // insertEdge does nothing. 

Pass g by pointer to insertEdge. Otherwise, insertEdge will modify a (shallow) copy of your graph, which is not what you want. So the type of parameter g should be Graph*.

Here is a suitable heading for insertEdge.

 void insertEdge(vertexNum u, vertexNum v, int w, Graph* g) 

Make sure that insertEdge does the whole job of inserting an edge. Don't force its caller to do part of the job. Increasing the number of edges is part of the job.