Store distance table

Question

I have a distance table, which I want to represent as code. It stores the distances between points and has same row and column headings. An upper right part of the table is a mirrored part of the lower left. And there are empty cells at intersections of the same points. How should I represent these in code so I could be able to get/set distance values by row and column ids without duplicating the values?

Answer 1

You can utilise Dictionary with two towns as a key.
Wrap it within class to hide implementation details and expose one method where you can check for a towns in any orders, which gives possibility to have dictionary without duplicates.

public class Distances
{
    private readonly Dictionary<(string, string), int> _distances;

    public Distances()
    {
        _distances = new Dictionary<(string, string), int>
       {
           { ("Eilat", "Ashkelton"), 307 }
       };
    }

    public int? FindBetween(string town1, string town2)
    {
        if (_distances.TryGetValue((town1, town2), out var distance1))
        {
            return distance1;
        }

        if (_distances.TryGetValue((town2, town1), out var distance2))
        {
            return distance2;
        }

        return null;
    }
}

Usage

var distances = new Distances();

var distance = distances.FindBetween("Eilat", "Ashkelton"); // 307