vector insert() Function in C++ STL

std::vector::insert() is a built-in function in C++ STL that inserts new elements before the element at the specified position, effectively increasing the container size by the number of elements inserted.

Time Complexity – Linear, O(N)

The insert function is overloaded to work on multiple cases which are as follows:

1. Insert an element at the given index.
2. Insert an element multiple times.
3. Insert a range of elements at the given index.

1. Insert an Element at the Given Index

Syntax of insert() in Vector

vector_name.insert (position, val);

Parameters

The function accepts two parameters specified below:

• position – It specifies the iterator which points to the position where the insertion is to be done.
• val – It specifies the value to be inserted.

Example of insert() in vector

C++

// C++ program to illustrate the function of
// vector_name.insert(position,val)
#include <bits/stdc++.h>
using namespace std;

int main()
{

    // Initialising the vector
    vector<int> vector_name{ 1, 2, 3, 4, 5 };

    // Printing out the original vector
    cout << "Original vector :\n";
    for (auto x : vector_name)
        cout << x << " ";
    cout << "\n";

    // Inserting the value 100 at position 3(0-based
    // indexing) in the vector
    vector_name.insert(vector_name.begin() + 3, 100);

    // Printing the modified vector
    cout << "Vector after inserting 100 at position 3 :\n";
    for (auto x : vector_name)
        cout << x << " ";
    cout << "\n";

    // Inserting the value 500 at position 1(0-based
    // indexing) in the vector
    vector_name.insert(vector_name.begin() + 1, 500);

    // Printing the modified vector
    cout << "Vector after inserting 500 at position 1 :\n";
    for (auto x : vector_name)
        cout << x << " ";
    return 0;
}

// This code is contributed by Abhijeet Kumar(abhijeet19403)

Output

Original vector :
1 2 3 4 5 
Vector after inserting 100 at position 3 :
1 2 3 100 4 5 
Vector after inserting 500 at position 1 :
1 500 2 3 100 4 5 

2. Insert Multiple Elements at Given Index

Syntax of insert() in Vector

vector_name.insert(position, size, val)

Parameters

The function accepts three parameters specified as below:

• position – It specifies the iterator which points to the position where the insertion is to be done.
• size – It specifies the number of times a val is to be inserted at the specified position.
• val – It specifies the value to be inserted.

Example of insert() in Vector

C++

// C++ program to illustrate the function of
// vector_name.insert(position,size,val)
#include <bits/stdc++.h>
using namespace std;

int main()
{

    // Initialising the vector
    vector<int> vector_name{ 1, 2, 3, 4, 5 };

    // Printing out the original vector
    cout << "Original vector :\n";
    for (auto x : vector_name)
        cout << x << " ";
    cout << endl;

    // Inserting the value 100, 4 times starting at position
    // 3
    vector_name.insert(vector_name.begin() + 3, 4, 100);

    // Printing the modified vector
    cout << "Vector after inserting 100, 4 times, starting "
            "at position 3 :\n";
    for (auto x : vector_name)
        cout << x << " ";
    return 0;
}

// This code contributed by Harsh Singh (hsnooob)

Output

Original vector :
1 2 3 4 5 
Vector after inserting 100, 4 times, starting at position 3 :
1 2 3 100 100 100 100 4 5 

3. Insert the Range of Elements at Given Index

Syntax of Vector insert()

vector_name.insert(position, iterator1, iterator2)

Parameters

The function accepts three parameters specified below:

• position – It specifies the position at which insertion is to be done in the vector.
• iterator1 – It specifies the starting position from which the elements are to be inserted
• iterator2 – It specifies the ending position till which elements are to be inserted

Example of Vector insert()

C++

// C++ program to illustrate the function of
// vector_name.insert(position,itr1,itr2)
#include <bits/stdc++.h>
using namespace std;

int main()
{

    // Initialising the vector
    vector<int> original{ 1, 2, 3, 4, 5 };

    vector<int> temp{ 2, 5, 9, 0, 3, 10 };

    // Printing out the original vector
    cout << "Original vector :\n";
    for (auto x : original)
        cout << x << " ";
    cout << endl;

    // Inserting the portion of temp vector in original
    // vector temp.begin()+3 is starting iterator of vector
    // to be copied temp.begin()+5 is ending iterator of
    // vector to be copied
    original.insert(original.begin() + 3, temp.begin() + 2,
                    temp.begin() + 5);

    // Printing the modified vector
    cout << "Vector after Inserting the portion of temp "
            "vector in original vector :\n";
    for (auto x : original)
        cout << x << " ";
    return 0;
}

// This code contributed by Harsh Singh (hsnooob)

Output

Original vector :
1 2 3 4 5 
Vector after Inserting the portion of temp vector in original vector :
1 2 3 9 0 3 4 5