vector::insert() function with example in C++ STL

C++ STL vector::insert() function: Here, we are going to learn about the insert() function of vector header in C++ STL with example.
Submitted by IncludeHelp, on May 16, 2019

C++ vector::insert() function

vector::insert() is a library function of "vector" header, it is used to insert elements in a vector, it accepts an element, set of elements with a default value or other values from other containers and insert in the vector from specified iterator position.

Note: To use vector, include <vector> header.

Syntax of vector::insert() function

    //inserting an element
    vector::insert(iterator position, value);

    //inserting multiple elements 
    vector::insert(iterator position, size, default_value);

    //inserting elements from other containers 
    vector::insert(iterator position, iterator start_position, iterator end_position);

Parameter(s):

In the case of inserting an element: iterator position, value – iterator position is the index using the iterator of the vector where an element to be added, value is an element.

In the case of inserting multiple elements: iterator position, size, default_value – iterator position is the index using iterator of the vector where elements to be added, size is the number of elements to be added and default_value is the value which will be inserted in the vector.

In the case of inserting elements from other containers: iterator position, iterator start_position, iterator end_position – iterator position is the index using iterator of the vector where elements to be added, start_position, iterator end_position are the iterators of another container whose value will be inserted in the current vector.

Return value:

In the case of inserting an element, it returns an iterator pointing to the first newly added element, and in other cases, it returns void.

Example:

    Input:
    //vector declaration
    vector<int> v1{ 10, 20, 30, 40, 50 };
    //array
    int x[] = { 1, 2, 3, 4, 5 };
    

    //inserting an element
    v1.insert(v1.begin() + 2, 100); //inserts 100 at 2nd index
    
    //inserting multiple elements with default value
    //inserts 5 elements (99) from 2nd index
	v1.insert(v1.begin() + 2, 5, 99);     
    //inserting array (other containers elements)
    
    //inserts 3 elements (from array) from 1st index
	v1.insert(v1.begin() + 1, x + 0, x + 3); 
    
    Output:
    v1: 10 1 2 3 20 99 99 99 99 99 100 30 40 50

C++ program to demonstrate example of vector::insert() function

//C++ STL program to demonstrate example of
//vector::insert() function

#include <iostream>
#include <vector>
using namespace std;

int main()
{
    //vector declaration
    vector<int> v1{ 10, 20, 30, 40, 50 };
    //array
    int x[] = { 1, 2, 3, 4, 5 };

    //printing elements
    cout << "before inserting the elements..." << endl;
    cout << "size of v1: " << v1.size() << endl;
    cout << "v1: ";
    for (int x : v1)
        cout << x << " ";
    cout << endl;

    //inserting an element
    v1.insert(v1.begin() + 2, 100); //inserts 100 at 2nd index

    //printing elements
    cout << "after inserting an element..." << endl;
    cout << "size of v1: " << v1.size() << endl;
    cout << "v1: ";
    for (int x : v1)
        cout << x << " ";
    cout << endl;

    //inserting multiple elements with default value
    //inserts 5 elements (99) from 2nd index
    v1.insert(v1.begin() + 2, 5, 99);

    //printing elements
    cout << "after inserting multiple elements..." << endl;
    cout << "size of v1: " << v1.size() << endl;
    cout << "v1: ";
    for (int x : v1)
        cout << x << " ";
    cout << endl;

    //inserting array (other containers elements)
    //inserts 3 elements (from array) from 1st index
    v1.insert(v1.begin() + 1, x + 0, x + 3);

    //printing elements
    cout << "after inserting multiple elements..." << endl;
    cout << "size of v1: " << v1.size() << endl;
    cout << "v1: ";
    for (int x : v1)
        cout << x << " ";
    cout << endl;

    return 0;
}

Output

before inserting the elements... 
size of v1: 5
v1: 10 20 30 40 50 
after inserting an element...
size of v1: 6
v1: 10 20 100 30 40 50 
after inserting multiple elements... 
size of v1: 11 
v1: 10 20 99 99 99 99 99 100 30 40 50
after inserting multiple elements... 
size of v1: 14 
v1: 10 1 2 3 20 99 99 99 99 99 100 30 40 50

Reference: C++ vector::insert()