I was reviewing a paper of a double-blind conference (ML/AI-based conference). The authors improved the approximation bounds for some special instances of a problem. To understand their proof better, I was thinking of a solution by myself while picking some hints from their proof. Using those hints, I came up with a better algorithm for the general instance of the problem. Moreover, my algorithm is much simpler than theirs.
I am feeling a bit greedy here; I want to suggest these changes to them and also want authorship in their paper. I can not ask them since I do not know them. I can not publish my own paper since a few ideas are borrowed from their proof and their manuscript is not online. What should I do?