How to convert generic sequence into triangle using LINQ?

Question

If I have a sequence IEnumerable<T> (not numbers, just T):

[ a, b, c, d ]

How to return sort of Pascal's or Floyd's triangle:

a
ab
abc
abcd

so it would be IEnumerable<IEnumerable<T>>?

Wondering whether there a way to achieve this elegantly using LINQ rather than implement manually using loops.

Answer 1

This should work:

var seq = new List<string> { "a", "b", "c", "d" };
var pascal = seq.Select(a => seq.Take(seq.IndexOf(a) +1 ).ToList());

edit:

var seq = new List<string> { "a", "b", "c", "d" };
var pascal = seq.Select((a,i) => seq.Take(i+1).ToList());