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There is an algorithm to sort 5 items in 7 comparisons: Design an efficient algorithm to sort 5 distinct keys in fewer than 8 comparisons
Does std::sort() use that algorithm if it is called for 5 items?
Can this algorithm be extended to 7 items? What is the fastest algorithm for sorting 7 integers in C/C++?
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The number of comparisons plays a more crucial role in sorting speed. 3) For small size data sets, Insertion sort is more efficient than Quicksort and Heapsort. 4) For large size data sets, Heapsort is better than the other twos, Heapsort is a better choice. In such a case, Insertion sort must be avoided.
Quicksort. Quicksort is one of the most efficient sorting algorithms, and this makes of it one of the most used as well. The first thing to do is to select a pivot number, this number will separate the data, on its left are the numbers smaller than it and the greater numbers on the right.
In general, std::sort is indeed faster than qsort because of a couple of these things: qsort operates on void* , which first requires a dereference, and second requires the size of the data type to perform the swaps. Therefore, the swap operation of qsort is done every byte.
It is not a part of the standard if std::sort should try to perform as few as possible comparisons for small sizes. Different implementations may do that but this will depend on the library you are using.
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