Skip to main content

std::deque insert() method

// (1) Non const version only
iterator insert( const_iterator pos, const T& value );

// (2) Non const version only
iterator insert( const_iterator pos, T&& value );

// (3) Non const version only
iterator insert( const_iterator pos, size_type count, const T& value );

// (4) Non const version only
template< class InputIt >
iterator insert( const_iterator pos, InputIt first, InputIt last );

// (5) Non const version only
iterator insert( const_iterator pos, std::initializer_list<T> ilist );

Inserts element(s) into the container, if the container doesn't already contain an element with an equivalent key.

  • (1-2) Inserts value before pos.

  • (3) Inserts count copies of the value before pos.

  • (4) Inserts elements from range [ first; last ) before pos.

    This overload participates in overload resolution only if InputIt qualifies as LegacyInputIterator, to avoid ambiguity with the overload (3).

    Undefined behaviour

    The behavior is undefined if first and last are iterators into *this.

  • (5) Inserts elements from initializer list ilist before pos.

    Undefined behaviour

    All iterators, including the past-the-end iterator, are invalidated. References are invalidated too, unless pos == begin() or pos == end(), in which case they are not invalidated.

Parameters​

  • pos - iterator before which the content will be inserted. pos may be the end() iterator
  • value - element value to insert
  • count - number of elemnts to insert
  • first, last - range of elements to insert
  • ilist - initializer list to insert the values from

Type requirements​

Return value​

  • (1-2) Iterator pointing to the inserted value.
  • (3) Iterator pointing to the first element inserted, or pos if count == 0.
  • (4) Iterator pointing to the first element inserted, or pos if first == last.
  • (5) Iterator pointing to the first element inserted, or pos if ilist is empty.

Complexity​

For all of the below N is std::min(std::distance(pos, begin()), std::distance(pos, end()))

  • (1-2) Linear in the lesser of the distances between pos and either of the ends of the container - O(N).
  • (3) Linear in count + linear in the lesser of the distances between pos and either of the ends of the container - O(count + N).
  • (4) Linear in std::distance(first, last) + linear in the lesser of the distances between pos and either of the ends of the container - O(std::distance(first, last) + N).
  • (5) Linear in ilist.size() + linear in the lesser of the distances between pos and either of the ends of the container - O(ilist.size() + N).

Exceptions​

If an exception is thrown when inserting a single element at either end, this function has no effect (strong exception guarantee).

Example​

Main.cpp
#include <iostream>
#include <iterator>
#include <deque>

void print(int id, const std::deque<int>& container)
{
    std::cout << id << ". ";
    for (const int x: container)
        std::cout << x << ' ';
    std::cout << '\n';
}

int main ()
{
    std::deque<int> c1(3, 100);
    print(1, c1);

    auto it = c1.begin();
    it = c1.insert(it, 200);
    print(2, c1);

    c1.insert(it, 2, 300);
    print(3, c1);

    // reset `it` to the begin:
    it = c1.begin();

    std::deque<int> c2(2, 400);
    c1.insert(std::next(it, 2), c2.begin(), c2.end());
    print(4, c1);

    int arr[] = {501, 502, 503};
    c1.insert(c1.begin(), arr, arr + std::size(arr));
    print(5, c1);

    c1.insert(c1.end(), {601, 602, 603});
    print(6, c1);
}
Possible output
1. 100 100 100
2. 200 100 100 100
3. 300 300 200 100 100 100
4. 300 300 400 400 200 100 100 100
5. 501 502 503 300 300 400 400 200 100 100 100
6. 501 502 503 300 300 400 400 200 100 100 100 601 602 603
This article originates from this CppReference page. It was likely altered for improvements or editors' preference. Click "Edit this page" to see all changes made to this document.
Hover to see the original license.