std::back_inserter

From cppreference.com
< cpp‎ | iterator
Defined in header <iterator>
template< class Container >
std::back_insert_iterator<Container> back_inserter( Container& c );
(until C++20)
template< class Container >
constexpr std::back_insert_iterator<Container> back_inserter( Container& c );
(since C++20)

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.

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

Possible implementation

template< class Container >
std::back_insert_iterator<Container> back_inserter( Container& c )
{
    return std::back_insert_iterator<Container>(c);
}

Example

#include <iostream>
#include <vector>
#include <algorithm>
#include <iterator>
 
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 << ' ';
}

Output:

1 2 3 4 5 6 7 8 9 10 -1 -1 -1

See also

iterator adaptor for insertion at the end of a container
(class template)
creates a std::front_insert_iterator of type inferred from the argument
(function template)
creates a std::insert_iterator of type inferred from the argument
(function template)