std::back_inserter
Min standard notice:
Header: <iterator>
back_inserter is a convenience function template that constructs a std::back_insert_iterator for the container c with the type deduced from the type of the argument.
# Declarations
template< class Container >
std::back_insert_iterator<Container> back_inserter( Container& c );
(constexpr since C++20)
# Parameters
c: container that supports a push_back operation
# Return value
A std::back_insert_iterator which can be used to add elements to the end of the container c.
# Example
#include <algorithm>
#include <iostream>
#include <iterator>
#include <vector>
int main()
{
std::vector<int> v{1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
std::fill_n(std::back_inserter(v), 3, -1);
for (int n : v)
std::cout << n << ' ';
std::cout << '\n';
}