I've had some interesting discussions in the past couple of days about problem solving and strategies. To start off, let me just say that I see these as the same thing. Problem solving is to get from point A, the problem, to point B, the solution, as effectively as possible.
Someone else pointed out how, "Everything is a... pattern." I agree with this as well, and I don't see a contradiction with everything being problem solving. I would also say that everything is a system.
You could see problem solving/strategy as the base unit of working on patterns/systems. It's a bit like matter and energy. Or yin and yang. Or data and processing. Two sides to the same coin.