3 ms·
I think people do say a hash table is O(1). It's the average time complexity (for some value of average) though, not the worst case.
by robertlagrant 23d ago
I think people do say a hash table is O(1). It's the average time complexity (for some value of average) though, not the worst case.
- jpitz 23d agoYeah but there's a formal term for average time complexity, Theta
- emil-lp 23d agoΘ does not usually mean average, but simultaneously upper and lower asymptotic bounds.
- xdavidliu 23d agoyou might want to read that chapter of CLRS again
- jpitz 22d agoYou're right. It isn't the average bound, it is the upper and lower bound stated together ( as long as thats the same function )
- lou1306 23d agoO(1) insertion is the amortized worst-case time complexity, actually. (Amortized in the sense that the O(n) cost of copying is paid only during the n-th insertion). Average complexity is a slightly different thing.
- d0mine 21d agoIt is not “worst-case” (as the post demonstrates, you can get worse results by using specifically crafted data that exploits hash collisions). There are algorithms that can get you O(logN) instead of O(N) even on such data.