But sorting has a known O(N log N) algorithm.  Nobody sorts by comparing all N! permutations and picking the correct one.  (Well, I certainly don&#x27;t.)<p>On the other hand, TSP almost certainly does not have any O(N^k) algorithm, for any fixed k.  Sure, the difference between (say) N^200 and N! is huge, but an introductory article cannot explain every details.<p>Saying that TSP is as hard as N! is technically wrong, but it&#x27;s much <i>less</i> wrong than saying sorting is as hard as N!.<p>His posts read more like an advertisement for his research area (optimization) than actual complaint.  Well, that&#x27;s not a bad thing, but I feel the title is a bit clickbait-ish...