NAME¶

std::vector::insert - std::vector::insert

Synopsis¶

iterator insert( const_iterator pos, const T& value ); (1) (constexpr since C++20)
iterator insert( const_iterator pos, T&& value ); (2) (since C++11)
(constexpr since C++20)
iterator insert( const_iterator pos, (3) (constexpr since C++20)
size_type count, const T& value );
template< class InputIt >
iterator insert( const_iterator pos, InputIt first, (4) (constexpr since C++20)
InputIt last );
iterator insert( const_iterator pos, (5) (since C++11)
std::initializer_list<T> ilist ); (constexpr since C++20)

Inserts elements at the specified location in the container.

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 has the same effect as overload (3) if InputIt is an (until C++11)
integral type.
This overload participates in overload resolution only if InputIt
qualifies as LegacyInputIterator, to avoid ambiguity with the overload (since C++11)
(3).

If first and last are iterators into *this, the behavior is undefined.
5) Inserts elements from initializer list ilist before pos.

If after the operation the new size() is greater than old capacity() a reallocation
takes place, in which case all iterators (including the end() iterator) and all
references to the elements are invalidated. Otherwise, only the iterators and
references before the insertion point remain valid.

Parameters¶

pos - iterator before which the content will be inserted
(pos may be the end() iterator)
value - element value to insert
count - number of elements to insert
first, last - the range of elements to insert, cannot be iterators
into container for which insert is called
ilist - initializer list to insert the values from

Type requirements¶

-
T must meet the requirements of CopyAssignable and CopyInsertable in order to use
overload (1).
-
T must meet the requirements of MoveAssignable and MoveInsertable in order to use
overload (2).
-
T must meet the requirements of CopyAssignable and CopyInsertable in order to use
overload (3).
-
T must meet the requirements of EmplaceConstructible in order to use overloads
(4,5).
-
T must meet the requirements of MoveAssignable and MoveInsertable in order to use
overload (4). required only if InputIt satisfies LegacyInputIterator but not
LegacyForwardIterator. (until C++17)
-
T must meet the requirements of Swappable, MoveAssignable, MoveConstructible and
MoveInsertable in order to use overloads (4,5). (since C++17)

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¶

1,2) Constant plus linear in the distance between pos and end of the container.
3) Linear in count plus linear in the distance between pos and end of the container.
4) Linear in std::distance(first, last) plus linear in the distance between pos and
end of the container.
5) Linear in ilist.size() plus linear in the distance between pos and end of the
container.

Exceptions¶

If an exception is thrown other than by

* the copy constructor of T,

* the move constructor of T, (since C++11)

* the copy assignment operator of T,

* the move assignment operator of T, (since C++11)

* any InputIt operation,

these functions have no effect (strong exception safety guarantee).

If an exception is thrown when inserting a single element at the end,
and T is CopyInsertable or
std::is_nothrow_move_constructible<T>::value is true, this function (since C++11)
has no effect (strong exception guarantee). Otherwise, if an exception
is thrown by the move constructor of a non-CopyInsertable T, the
effects are unspecified.

Example¶

// Run this code

#include <iostream>
#include <iterator>
#include <vector>

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

int main ()
{
std::vector<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);

// `it` no longer valid, get a new one:
it = c1.begin();

std::vector<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);
}

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

Defect reports

The following behavior-changing defect reports were applied retroactively to
previously published C++ standards.

DR Applied to Behavior as published Correct behavior
LWG 149 C++98 overloads (3) and (4) returned nothing returns an iterator
LWG 247 C++98 the complexity was only specified for specified for all
overload (3) overloads
the strong exception guarantee also
LWG 406 C++98 applied if no guarantee in this case
the exception is thrown by an InputIt
operation

See also¶

emplace constructs element in-place
(C++11) (public member function)
push_back adds an element to the end
(public member function)
inserter creates a std::insert_iterator of type inferred from the argument
(function template)