How to remove an element from the beginning in a vector if the order of elements is not important?.

Move the last element to the position of the removed element and reduce the size of the vector.

#include <vector>
#include <algorithm>

void remove_front_order_irrelevant(std::vector<int>& vec) {
    if (!vec.empty()) {
        std::swap(vec.front(), vec.back()); // Move the last element to the front
        vec.pop_back(); // Remove the last element (now the former first)
    }
}