C++ <list> - insert() Function
The C++ list::insert function is used to insert new elements before the element at the specified position. This results into increasing the list 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 list 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 list::insert function is used to insert elements in the given list.
#include <iostream>
#include <list>
using namespace std;
int main (){
list<int> list1 = {10, 20, 30};
list<int> list2 = {10, 20, 30};
list<int> list3 = {10, 20, 30};
list<int> list4 = {100, 200, 300};
list<int>::iterator it;
//single element version
it = list1.begin(); it++; //points to second element
list1.insert(it, 55);
//fill version - fill 3 new elements at specified location
it = list2.begin();
list2.insert(++it, 3, 55);
//range version
it = list3.begin();
list3.insert(++it, list4.begin(), list4.end());
cout<<"list1 contains: ";
for(it = list1.begin(); it != list1.end(); ++it)
cout<<*it<<" ";
cout<<"\nlist2 contains: ";
for(it = list2.begin(); it != list2.end(); ++it)
cout<<*it<<" ";
cout<<"\nlist3 contains: ";
for(it = list3.begin(); it != list3.end(); ++it)
cout<<*it<<" ";
return 0;
}
The output of the above code will be:
list1 contains: 10 55 20 30 list2 contains: 10 55 55 55 20 30 list3 contains: 10 100 200 300 20 30
Example:
The move version of the insert function can also be used to insert the content of one list into the another list. Consider the example below.
#include <iostream>
#include <list>
using namespace std;
int main (){
list<int> list1 = {10, 20, 30};
list<int> list2 = {100, 200, 300};
list<int>::iterator it;
//move version - moving content of list1 to list2
for(it = list1.begin(); it != list1.end(); ++it)
list2.insert(list2.end(), move(*it));
cout<<"list1 contains: ";
for(it = list1.begin(); it != list1.end(); ++it)
cout<<*it<<" ";
cout<<"\nlist2 contains: ";
for(it = list2.begin(); it != list2.end(); ++it)
cout<<*it<<" ";
return 0;
}
The output of the above code will be:
list1 contains: 10 20 30 list2 contains: 100 200 300 10 20 30
Example:
Similarly, the initializer list version can be used to insert elements in the given list.
#include <iostream>
#include <list>
using namespace std;
int main (){
list<int> MyList = {10, 20, 30};
list<int>::iterator it;
//initializer list version
initializer_list<int> ilist = {11, 22, 33, 44, 55};
it = MyList.begin();
MyList.insert(++it, ilist);
cout<<"MyList contains: ";
for(it = MyList.begin(); it != MyList.end(); ++it)
cout<<*it<<" ";
return 0;
}
The output of the above code will be:
MyList contains: 10 11 22 33 44 55 20 30
❮ C++ <list> Library
