Select all unique combinations of a single list, with no repeats, using LINQ
I have a list of numbers, and I need to create every possible unique combination of the numbers in the list, without repeats, using a LINQ query. So, for example, if I have { 1, 2, 3 } , the combinations would be 1-2 , 1-3 , and 2-3 .
I currently use two for loops, like so:
for (int i = 0; i < slotIds.Count; i++)
{
for (int j = i + 1; j < slotIds.Count; j++)
{
ExpressionInfo info1 = _expressions[i];
ExpressionInfo info2 = _expressions[j];
// etc...
}
}
Is it possible to convert these two for loops to LINQ?
Thanks.
Sure - you can do it in a single call to SelectMany with an embedded call to Skip :
var query = slotIds.SelectMany((value, index) => slotIds.Skip(index + 1),
(first, second) => new { first, second });
Here's an alternative option, which doesn't use quite such an esoteric overload of SelectMany :
var query = from pair in slotIds.Select((value, index) => new { value, index })
from second in slotIds.Skip(pair.index + 1)
select new { first = pair.value, second };
These do basically the same thing, just in slightly different ways.
Here's another option which is much closer to your original:
var query = from index in Enumerable.Range(0, slotIds.Count)
let first = slotIds[index] // Or use ElementAt
from second in slotIds.Skip(index + 1)
select new { first, second };
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