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What would be the best way to check that a std::vector is sorted? Is there something faster than a loop checking that v[i]<=v[i+1]? Is it faster/cleaner with iterators? Or is it actually better to just call sort every time (though the "v is already sorted" case is quite common)?
We can safely assume the vector only contains PODs, usually floats and sometimes doubles and ints.
The size of the vector is non-trivial (usually a few thousands items) but not extreme (not gigabyte-sized).
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if (result == false) cout << "Vector elements are not sorted in ascending order." << endl; result = is_sorted(v.
Sorting a vector in C++ Sorting a vector in C++ can be done by using std::sort(). It is defined in<algorithm> header. To get a stable sort std::stable_sort is used. It is exactly like sort() but maintains the relative order of equal elements.
unsorted() function in R Language is used to check if an object is sorted or not. It returns False if the object is sorted otherwise True. Here, the output is FALSE for vector because it is sorted and matrix is unsorted, hence the function returns TRUE for matrix.
The vector can use the array notation to access the elements. If you don't want to use the default std::sort , or std::sort with custom comparator, you can use qsort or write your own.
Is there something faster than a loop checking that v[i]<=v[i+1] ?
No.
If this is something you wish to check often, you might want to make a wrapper class that keeps a "sorted" flag which starts out False, is set to False whenever an item is added, and add a member function sort() that sets the flag to True after sorting.
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The best way is to use std::is_sorted:
is_sorted(v.begin(), v.end())
:-)
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