C++ <deque> - insert() Function
The C++ deque::insert function is used to insert new elements before the element at the specified position. This results into increasing the deque size by the number of elements inserted.
Syntax
//single element version iterator insert (iterator position, const value_type& val); //fill version void insert (iterator position, size_type n, const value_type& val); //range version template <class InputIterator> void insert (iterator position, InputIterator first, InputIterator last);
//single element version iterator insert (const_iterator position, const value_type& val); //fill version iterator insert (const_iterator position, size_type n, const value_type& val); //range version template <class InputIterator> iterator insert (const_iterator position, InputIterator first, InputIterator last); //move version iterator insert (const_iterator position, value_type&& val); //initializer list version iterator insert (const_iterator position, initializer_list<value_type> ilist);
Parameters
position |
Specify the iterator position in the deque where the new elements need to be inserted. |
val |
Specify the value to be inserted. |
n |
Specify the number of new elements to be inserted. |
first |
Specify the starting position of InputIterator. Copies of the elements in the range [first,last) are inserted at position (in the same order). |
last |
Specify the last position of InputIterator. Copies of the elements in the range [first,last) are inserted at position (in the same order). |
ilist |
Specify the initializer_list object. |
Return Value
Returns an iterator which points to the first element of the newly inserted elements.
Time Complexity
Linear i.e, Θ(n)
Example:
In the example below, the deque::insert function is used to insert elements in the given deque.
#include <iostream>
#include <deque>
using namespace std;
int main (){
deque<int> deque1 = {10, 20, 30};
deque<int> deque2 = {10, 20, 30};
deque<int> deque3 = {10, 20, 30};
deque<int> deque4 = {100, 200, 300};
deque<int>::iterator it;
//single element version
it = deque1.begin();
deque1.insert(it + 2, 55);
//fill version - fill 3 new elements at specified location
it = deque2.begin();
deque2.insert(it + 2, 3, 55);
//range version
it = deque3.begin();
deque3.insert(it+2, deque4.begin(), deque4.end());
cout<<"deque1 contains: ";
for(it = deque1.begin(); it != deque1.end(); ++it)
cout<<*it<<" ";
cout<<"\ndeque2 contains: ";
for(it = deque2.begin(); it != deque2.end(); ++it)
cout<<*it<<" ";
cout<<"\ndeque3 contains: ";
for(it = deque3.begin(); it != deque3.end(); ++it)
cout<<*it<<" ";
return 0;
}
The output of the above code will be:
deque1 contains: 10 20 55 30 deque2 contains: 10 20 55 55 55 30 deque3 contains: 10 20 100 200 300 30
Example:
The move version of the insert function can also be used to insert the content of one deque into the another deque. Consider the example below.
#include <iostream>
#include <deque>
using namespace std;
int main (){
deque<int> deque1 = {10, 20, 30};
deque<int> deque2 = {100, 200, 300};
deque<int>::iterator it;
//move version - moving content of deque1 to deque2
for(int i = 0; i < deque1.size(); i++)
deque2.insert(deque2.begin() + i, move(*(deque1.begin()+i)));
cout<<"deque1 contains: ";
for(it = deque1.begin(); it != deque1.end(); ++it)
cout<<*it<<" ";
cout<<"\ndeque2 contains: ";
for(it = deque2.begin(); it != deque2.end(); ++it)
cout<<*it<<" ";
return 0;
}
The output of the above code will be:
deque1 contains: 10 20 30 deque2 contains: 10 20 30 100 200 300
Example:
Similarly, the initializer list version can be used to insert elements in the given deque.
#include <iostream>
#include <deque>
using namespace std;
int main (){
deque<int> dq = {10, 20, 30};
deque<int>::iterator it;
//initializer list version
initializer_list<int> MyList = {11, 22, 33, 44, 55};
it = dq.begin();
dq.insert(it+2, MyList);
cout<<"dq contains: ";
for(it = dq.begin(); it != dq.end(); ++it)
cout<<*it<<" ";
return 0;
}
The output of the above code will be:
dq contains: 10 20 11 22 33 44 55 30
❮ C++ <deque> Library
