Fastest solution to list all pairs of n integers?

Question

I want to list all possible pairs of the integers [1, n] with a large n. I find myself looking for the fastest option. This is what I\'ve come up w

Answer 1

To replace nchoosek(1:N,2)

With bsxfun -

[Y,X] = find(bsxfun(@gt,[1:N]',[1:N]))
pair = [X, Y];

With tril and find only (without ind2sub) -

[y,x] = find(tril(true(N),-1))
pair = [X, Y];