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vector insert() function in C++ STL

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  • Difficulty Level : Easy
  • Last Updated : 11 Jan, 2023
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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)

  1. Syntax:
vector_name.insert (position, val)
  1. Parameter: The function accepts two parameters specified as 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.

C++




// A 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. Syntax:

vector_name.insert(position, size, val)
  1. Parameter: 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.

      3. Syntax:

vector_name.insert(position, iterator1, iterator2)
  1. Parameter: The function accepts three parameters specified as 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

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