[C++ STL] map faster than unordered_map?

Revision en1, by Mridul323, 2020-12-03 22:07:05

Hello Codeforces!

Recently I was trying to solve problem 1102E — Monotonic Renumeration

I tried submitting my solution 100299607 using unordered_map and got TLE on test 47. Then I went thorough the other solutions and found that people have solved it using map. I submitted same code again 100299556 using map and this got Accepted.

I used to think that unordered_map is always faster than the map. I googled and then get to know that search time of map is O(log(n)) while search time of unordered_map in O(1) and in worst case its O(n).

Internally unordered_map is implemented using Hash Table so how the search time can take O(n) in worst case?

Somebody please clear my doubt.

Thanks

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en1 English Mridul323 2020-12-03 22:07:05 768 Initial revision (published)