std::vector::insert

 

C++

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

Inserts elements at specified location in the container.

1-2) inserts value before the location pointed to by pos

3) inserts count copies of the value before the location pointed to by pos

4) inserts elements from range [first, last) before the location pointed to by pos. This overload does not participate in overload resolution if InputIt does not satisfy InputIterator. (since C++11) The behavior is undefined if first and last are iterators into *this.

5) inserts elements from initializer list ilist.

Causes reallocation if the new size() is greater than the old capacity(). If the new size() is greater than capacity(), all iterators and references are invalidated. Otherwise, only the iterators and references before the insertion point remain valid. The past-the-end iterator is also invalidated.

Parameters

pos	-	iterator to the location before which the content will be inserted. pos may be the end() iterator
value	-	element value to insert
first, last	-	the range of elements to insert, can't be iterators into container for which insert is called
ilist	-	initializer list to insert the values from
Type requirements
- InputIt must meet the requirements of InputIterator.

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 when inserting a single element at the end, and T is CopyInsertable or std::is_nothrow_move_constructible<T>::value is true, there are no effects (strong exception guarantee).

Example

Run this code

#include <iostream>
#include <vector>
 
void print_vec(const std::vector<int>& vec)
{
    for (auto x: vec) {
         std::cout << ' ' << x;
    }
    std::cout << '\n';
}
 
int main ()
{
    std::vector<int> vec(3,100);
    print_vec(vec);
 
    auto it = vec.begin();
    it = vec.insert(it, 200);
    print_vec(vec);
 
    vec.insert(it,2,300);
    print_vec(vec);
 
    // "it" no longer valid, get a new one:
    it = vec.begin();
 
    std::vector<int> vec2(2,400);
    vec.insert(it+2, vec2.begin(), vec2.end());
    print_vec(vec);
 
    int arr[] = { 501,502,503 };
    vec.insert(vec.begin(), arr, arr+3);
    print_vec(vec);
}

Output:

100 100 100
200 100 100 100
300 300 200 100 100 100
300 300 400 400 200 100 100 100
501 502 503 300 300 400 400 200 100 100 100

See also

emplace (C++11)	constructs element in-place (public member function)
push_back	adds elements to the end (public member function)