public member function
<list>

std::list::insert

single element (1)
iterator insert (iterator position, const value_type& val);
fill (2)
    void insert (iterator position, size_type n, const value_type& val);
range (3)
template <class InputIterator>
    void insert (iterator position, InputIterator first, InputIterator last);
single element (1)
iterator insert (const_iterator position, const value_type& val);
fill (2)
iterator insert (const_iterator position, size_type n, const value_type& val);
range (3)
template <class InputIterator>
iterator insert (const_iterator position, InputIterator first, InputIterator last);
move (4)
iterator insert (const_iterator position, value_type&& val);
initializer list (5)
iterator insert (const_iterator position, initializer_list<value_type> il);
Insert elements
The container is extended by inserting new elements before the element at the specified position.

This effectively increases the list size by the amount of elements inserted.

Unlike other standard sequence containers, list and forward_list objects are specifically designed to be efficient inserting and removing elements in any position, even in the middle of the sequence.

The arguments determine how many elements are inserted and to which values they are initialized:

Parameters

position
Position in the container where the new elements are inserted.
iterator is a member type, defined as a bidirectional iterator type that points to elements.
val
Value to be copied (or moved) to the inserted elements.
Member type value_type is the type of the elements in the container, defined in list as an alias of its first template parameter (T).
n
Number of elements to insert. Each element is initialized to a copy of val.
Member type size_type is an unsigned integral type.
first, last
Iterators specifying a range of elements. Copies of the elements in the range [first,last) are inserted at position (in the same order).
Notice that the range includes all the elements between first and last, including the element pointed by first but not the one pointed by last.
The function template argument InputIterator shall be an input iterator type that points to elements of a type from which value_type objects can be constructed.
il
An initializer_list object. Copies of these elements are inserted at position (in the same order).
These objects are automatically constructed from initializer list declarators.
Member type value_type is the type of the elements in the container, defined in list as an alias of its first template parameter (T).

Return value

An iterator that points to the first of the newly inserted elements.

Member type iterator is a bidirectional iterator type that points to elements.

The storage for the new elements is allocated using the container's allocator, which may throw exceptions on failure (for the default allocator, bad_alloc is thrown if the allocation request does not succeed).

Example

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// inserting into a list
#include <iostream>
#include <list>
#include <vector>

int main ()
{
  std::list<int> mylist;
  std::list<int>::iterator it;

  // set some initial values:
  for (int i=1; i<=5; ++i) mylist.push_back(i); // 1 2 3 4 5

  it = mylist.begin();
  ++it;       // it points now to number 2           ^

  mylist.insert (it,10);                        // 1 10 2 3 4 5

  // "it" still points to number 2                      ^
  mylist.insert (it,2,20);                      // 1 10 20 20 2 3 4 5

  --it;       // it points now to the second 20            ^

  std::vector<int> myvector (2,30);
  mylist.insert (it,myvector.begin(),myvector.end());
                                                // 1 10 20 30 30 20 2 3 4 5
                                                //               ^
  std::cout << "mylist contains:";
  for (it=mylist.begin(); it!=mylist.end(); ++it)
    std::cout << ' ' << *it;
  std::cout << '\n';

  return 0;
}

Output:
mylist contains: 1 10 20 30 30 20 2 3 4 5

Complexity

Linear in the number of elements inserted (copy/move construction).

Iterator validity

No changes.

Data races

The container is modified.
No contained elements are accessed. Concurrently accessing or modifying different elements is safe, although iterating ranges that include position is not.

Exception safety

Strong guarantee: if an exception is thrown, there are no changes in the container.
If allocator_traits::construct is not supported with the appropriate arguments for the element constructions, or if an invalid position or range is specified, it causes undefined behavior.

See also

list::splice
Transfer elements from list to list (public member function )
list::merge
Merge sorted lists (public member function )
list::push_back
Add element at the end (public member function )
list::push_front
Insert element at beginning (public member function )
list::erase
Erase elements (public member function )

C++