Questions regarding well-defined instructions for completing a task, and relevant analysis in terms of time/memory/etc.
Questions tagged with ds.algorithms are generally asking an algorithm for a specific task, or asking to analyze some specific algorithm (different types of analysis are listed in this topic).
In the former case, it is possible to ask an algorithm for a specific task, whose resource (time/memory/etc.) consumption is somehow bounded.
Questions which seek the intrinsic difficulty of some problem (rather than some specific algorithm) are better be tagged with
cc.complexity-theory.
