Question

I have a DAG in a JSON format, where each node is an entry: it has a name, and two arrays. One array is for other nodes with arrows coming into it, another array for nodes that this node is directed towards (outgoing arrows).

So, for example:

{ 
  'id': 'A',   
  'connected_from' : ['B','C'],  
  'connects_to' : ['D','E']
}

And I have a collection of these nodes, that all together form a DAG.

I’d like to map the nodes to a struct to hold these nodes, where the id is simply a string, and I’d like the arrays to be vectors of pointers of this struct:

struct node { 
    string id;  
    vector<node*> connected_from;
    vector<node*> connected_to;
}

How do I convert the node entries as ‘id’ in the arrays of the JSON to a pointer to the correct struct holding that node?

One obvious approach is to build a map of key-value pairs, where key = id, value = the pointer to the struct with that id, and do a lookup – but is there a better way?

Answer 1

no, given only the information that you’ve provided there isn’t a better way: you need to build a map.

however, for single letter id’s the map can possibly take the form of a simple array with e.g. 26 entries for the English alphabet.