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Category Archives: STL

Use STL lower_bound even though it’s slower


Summarizing the last few posts on STL lower_bound: instead of falling back to a naive algorithm when it’s not given a random-access iterator, STL’s lower_bound algorithm still performs binary search using bidirectional or forward-only iterators. This causes it to perform 2N list traversals, which is four times as many as the naive algorithm’s average case […]

STL lower_bound is better for complex keys, but still loses on large N


Testing a list<int> is pretty much the worst possible case for STL’s lower bound algorithm. Recall from the analysis that STL’s lower_bound uses a binary search algorithm even when the cost of advancing an iterator N steps is O(N). The advantage of this algorithm is that it only performs O( log N ) comparisons, as […]

STL lower_bound on lists four times slower than naive algorithm


Here is a comparison between the naive lower bound and STL’s version. Execution time reported in seconds was measured using the Windows high resolution timer. An STL list of integers 1-N was created by populating a vector, shuffling it, pushing the elements onto a list, and sorting the list. This was done so the list […]