Combination of pairs / Unique pairs?

[SuperJMN]

I would like something like Cartesian, but considering that (a, b) <==> (b, a).

So you would simply create a distance matrix with some code like:

var distances = cities.UniquePairs(cities, (a, b) => (A: a, B: b, Distance: Random.Shared(200)));

[atifaziz]

I think you might looking for Subsets and specifically the overload that accepts a size. If you use a size of 2, you should get your unique pairs.

using System;
using System.Linq;
using MoreLinq;

var cities = new[]
{
    "New York",
    "Los Angeles",
    "Chicago",
    "Houston",
    "Phoenix"
};

var data =
    from e in cities.Subsets(2).Zip(MoreEnumerable.Random(200))
    select (e.First[0], e.First[1], e.Second);

foreach (var (a, b, distance) in data)
    Console.WriteLine($"({a}, {b}) -> Distance: {distance}");

This should produce the output:

(New York, Los Angeles) -> Distance: 181
(New York, Chicago) -> Distance: 115
(New York, Houston) -> Distance: 72
(New York, Phoenix) -> Distance: 68
(Los Angeles, Chicago) -> Distance: 108
(Los Angeles, Houston) -> Distance: 36
(Los Angeles, Phoenix) -> Distance: 50
(Chicago, Houston) -> Distance: 19
(Chicago, Phoenix) -> Distance: 21
(Houston, Phoenix) -> Distance: 140