Moving a vector element to the back of the vector

Question

Is there any better way (either faster or with fewer symbols of code) than erasing the element and re-adding it to the back?

template <typename T> void moveItemToBack(std::vector<T>& v, size_t itemIndex) {    T tmp(v[itemIndex]);    v.erase(v.begin() + itemIndex);    v.push_back(tmp); } 

Answer 1

You can do this with std::rotate from the standard library. Since this doesn't change the vector size it also won't trigger a reallocation. Your function would look something like this:

template <typename T> void moveItemToBack(std::vector<T>& v, size_t itemIndex) {     auto it = v.begin() + itemIndex;     std::rotate(it, it + 1, v.end()); } 

Answer 2

Possibly the fastest way, would be to swap it with the last element

template <typename T> void moveItemToBack(std::vector<T>& v, size_t itemIndex) {    std::swap(v[itemIndex], v.back()); // or swap with *(v.end()-1) } 

one operation! Ofcourse std::swap has to work with T