insert

Header

iterator insert(iterator it, const T& x = T()) 

The above inserts object x into the vector container at the position specified by iterator it. This version of the member function insert returns an iterator that points to the position where the new element was inserted into the vector.

void insert(iterator it, size_type n, const T& x)

This inserts n copies of object x into the vector container, starting at the position specified by iterator it.

void insert(iterator it, const_iterator first, const_iterator last)

This inserts the objects specified by the range [first, last) into the vector container, starting at the position specified by iterator it.

Any insertion operation can be expensive. To perform an insertion in the middle of a container, memory must be allocated at the start and end of the container. Then a bulk copy is performed to open space in the middle, at the location pointed to by the it argument. Finally, the data is copied into the new location. The function becomes more costly as the size of the container increases.

Inserting an element invalidates all iterators and references.

Sample

#include <vector>
#include <iostream>

int main()
{
	//default constructor
	std::vector<int> c1 ;

	//create vector with 10 copies of 4
	std::vector<int> c2(10, 4) ;

	//copy constructor
	std::vector<int> c3(c2) ;

	

	int ai[] = {0, 1, 2, 3, 4, 5} ;
	int i ;

	//range copy constructor
	std::vector<int> c4(ai, ai+5) ;
	
	std::vector<int> c5 ;

	//push_back
	for(i = 0; i < 5; i++)
		c5.push_back(ai[i]) ;

	//get_allocator
	std::vector<int>::allocator_type a1 = c4.get_allocator() ;

	//begin, end
	std::cout << "c4 (using begin, end) = " ;
	std::vector<int>::iterator Iter ;
	for(Iter = c4.begin(); Iter != c4.end(); Iter++)
		std::cout << *Iter << ", " ;
	std::cout << std::endl ;

	//rbegin, rend
	std::cout << "c4 (using rbegin, rend) = " ;
	std::vector<int>::reverse_iterator RevIter ;
	for(RevIter = c4.rbegin(); RevIter != c4.rend(); RevIter++)
		std::cout << *RevIter << ", " ;
	std::cout << std::endl ;

	//assign
	c2.assign(ai, ai+4) ;

	c1.assign(10, 4) ;

	//at
	std::cout << "third element in c1 = " << c1.at(3) << std::endl ;

	//operator[]
	std::cout << "c4[3] = " << c4[3] << std::endl ;

	//back
	std::cout << "last element in c2 = " << c2.back() << std::endl ;

	//front
	std::cout << "first element in c2 = " << c2.front() << std::endl ;

	//size
	std::cout << "number of elements in c2 = " << c2.size() << std::endl ;

	//max_size
	std::cout << "max number of elements c2 can hold using current allocator = " 
		<< c2.max_size() << std::endl ;

	//erase
	c3.erase(c3.begin(), c3.begin() + 4) ;

	//clear
	c2.clear() ;

	//empty
	if (c2.empty() == true)
		std::cout << "c2 is now empty" << std::endl ;

	//resize
	c2.resize(10, 30) ;
	std::cout << "number of elements in c2 = " << c2.size() << std::endl ;
	std::cout << "last element in c2 = " << c2.back() << std::endl ;
	std::cout << "first element in c2 = " << c2.front() << std::endl ;

	//reserve, capacity
	c2.reserve(70) ;
	std::cout << "current capacity of c2 = " 
		<< c2.capacity() << std::endl ;

	//pop_back
	c2.pop_back() ;
	std::cout << "last element in c2 = " << c2.back() << std::endl ;

	//swap
	c3.swap(c2) ;
	std::cout << "number of elements in c3 = " << c3.size() << std::endl ;
	std::cout << "last element in c3 = " << c3.back() << std::endl ;
	std::cout << "first element in c3 = " << c3.front() << std::endl ;

	//insert
	c1.insert(c1.begin(), 20) ;
	c1.insert(c1.begin()+1, 4, 10) ;
	c1.insert(c1.begin()+2, c5.begin(), c5.end()) ;
	std::cout << "c1 = " ;
	for(Iter = c1.begin(); Iter != c1.end(); Iter++)
		std::cout << *Iter << ", " ;
	std::cout << std::endl ;

	return 0 ;
}

Program Output

c4 (using begin, end) = 0, 1, 2, 3, 4,
c4 (using rbegin, rend) = 4, 3, 2, 1, 0,
third element in c1 = 4
c4[3] = 3
last element in c2 = 3
first element in c2 = 0
number of elements in c2 = 4
max number of elements c2 can hold using current allocator = 1073741823
c2 is now empty
number of elements in c2 = 10
last element in c2 = 30
first element in c2 = 30
current capacity of c2 = 70
last element in c2 = 30
number of elements in c3 = 9
last element in c3 = 30
first element in c3 = 30
c1 = 20, 10, 0, 1, 2, 3, 4, 10, 10, 10, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,