Question

I’m sorry for the tricky title, here is the example

graph main_graph = //initialize graph
graph sub_graph = //pick a subset of edges from the main_graph
while ( ! sub_graph.size() == 0) {
    select_edge();    //here I pick an edge basing on some heuristics
    reduce_graph();   //here I remove some edges from the main_graph
    sub_graph = //pick a subset of edges from the main_graph
}

So the point is that I have to write the very same code to define the sub_graph before entering the loop (because it could be already empty) and right before entering a new iteration.
This would not be that bad, if it wasn’t that I actually have three nested loops with the same problem, and the code to inizialize the sub_graph is a bunch of lines of code, so my code would look a lot replicated.

Any suggestion on how to better design this loop(s)? I have no restrictions (can use for, do-while…)

Even if this is pseudo-code, since is more a ‘design’ question, I’m coding in C++!

Answer 1

To avoid repeating lots of code, put the code in a function:

graph calc_subgraph(...) {...}

Then use it to initialize and recalculate your values:

for (graph subgraph = calc_subgraph(...); subgraph.size() != 0; subgraph = calc_subgraph(...))