Sorting has a simple local optimum implies global optimum property. If a list is sorted than any (not necessarily sequential) sublist is sorted, and the converse. No such property applies to TSP.
I think that the best way to think about why some combinatorial problems are hard and others easy isn't to ask what makes a problem hard, but rather what makes a problem easy. Combinatorial problems seem to be hard by default. It takes some special simplifying property to make them easy.
I think that the best way to think about why some combinatorial problems are hard and others easy isn't to ask what makes a problem hard, but rather what makes a problem easy. Combinatorial problems seem to be hard by default. It takes some special simplifying property to make them easy.