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In C++11 I use std::next because If I want to change vector to list, I dont have to change the rest of code.
For list, std::next is O(n), because I need to iterate all elements. But how is it for a vector? I have found this note on cppreference:
However, if
InputItorForwardItadditionally meets the requirements of LegacyRandomAccessIterator, complexity is constant.
Does vector meet these requirements? And why "Legacy"?
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You can use std::next. Show activity on this post. In case you use the vector as a circular list (that is, you consider the first element as the "next" of the last element), you can use the modulo operator against the length of the vector.
std::next in C++ std::next returns an iterator pointing to the element after being advanced by certain no. of positions. It is defined inside the header file . It does not modify its arguments and returns a copy of the argument advanced by the specified amount.
1) std::vector is a sequence container that encapsulates dynamic size arrays. 2) std::pmr::vector is an alias template that uses a polymorphic allocator. The elements are stored contiguously, which means that elements can be accessed not only through iterators, but also using offsets to regular pointers to elements.
std::next. Return the n th successor of iterator it .
There is a plan of adding concepts (compile time type constraints) in C++20. The new standard is supposed to contain concepts like InputIterator or RandomAccessIterator. To distinguish between the concepts and the old trait-like requirements cppreference uses LegacyRandomAccessIterator and so on for pre-concept requirements and RandomAccessIterator and so for concept requirements.
And so yes, std::vector::iterator meets requirements of LegacyRandomAccessIterator and actually will be fulfilling RandomAccessIterator concept as well. This leads straight to conclusion that std::next called on vector::iterator has complexity O(1).
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