Insert Multiple Elements at Given Positions in a Vector

What is a Vector in C++?

A vector is a dynamic array as the size of the vector changes during the program's execution. If we insert more elements in the vector it expands its size and if we remove elements from the vector it shrinks in size. A vector is part of the Standard Template Library (STL).

Problem Description

In this problem, we are given a vector and have to insert an element at a certain position. In this article, we are going to learn how to insert multiple positions in a vector in C++ using different approaches. Below are some examples to understand the problem clearly:

Example 1

  • Input 
    array = {10, 20, 30, 40, 50}
    Insert 15 at position 1
    Insert 25 at position 3
  • Output 
    array = {10, 15, 20, 25, 30, 40, 50}

Explanation:

If we insert element 15 at position 1 it will be inserted at index 1 and lie between 10 and 20 and if we insert element 15 at position 3 it will be inserted at index 3 and lies between 10 and 20.

Example 2

  • Input
    array = {1, 3, 7, 9, 11}
    Insert 4 at position 2
    Insert 8 at position 4
  • Output
    array = {1, 3, 4, 7, 8, 9, 11}

Explanation:

If we insert element 4 at position 2, it will be inserted at index 2 and lie between 3 and 7. If we insert element 8 at position 4, it will be inserted at index 4 and lies between 7 and 9.

Example 3

  • Input
    array = {2, 4, 6, 8, 10}
    Insert 3 at position 2
    Insert 7 at position 4
  • Output
    array = {2, 3, 4, 6, 7, 8, 10}

Explanation:

If we insert element 3 at position 2, it will be inserted at index 2 and lie between 2 and 4. If we insert element 7 at position 4, it will be inserted at index 4 and lies between 6 and 8.

Approaches

We will see and use different approaches for inserting multiple elements at given positions in a vector. Below are given three different approaches to it.

Using insert() Method

This is the simplest approach for inserting a single element at any given position in a vector or a range of elements at a specific position in the vector. In this approach, we can insert an element using the insert() method at any specific position where we want to insert.

Syntax for Inserting Single Element

vector.insert(position, value);
Where,
position is the index, where we want to insert the element.
value is the element we want to insert.

Syntax for Inserting Multiple Elements

vector.insert(position, start_iterator, end_iterator);
Where,
position is the index, where we want to insert the element.
start_iterator is an iterator that points to the first element to be inserted.
end_iterator is an iterator that points to the last element to be inserted.

Implementation Code

#include<bits/stdc++.h>
using namespace std;
int main() {
  vector < int > vec = {
    10,
    20,
    30,
    40,
    50
  };

  vec.insert(vec.begin() + 1, 15);
  vec.insert(vec.begin() + 3, 25);
  for (int i = 0; i < vec.size(); i++) {
    cout << vec[i] << " ";
  }
  return 0;
}

Output

10 15 20 25 30 40 50
Time Complexity: O(n)
Space Complexity: O(1)

Using emplace() Method

This approach is more efficient than the insert() method. Using this approach, we can directly insert elements at the given position of the vector. This method allows for in-place construction of elements. It constructs the aspect in the vector without needing to copy it.

Syntax for Inserting Single Element

vector.emplace(position, value);
Where,
position is the index, where we want to insert the element.
value is the element we want to insert.

Syntax for Inserting Multiple Elements

vector.emplace(position, value1);
vector.emplace(position, value2);
We repeat the above for each element we want to insert.
Where,
position is the index, where we want to insert the element.
value is the element we want to insert.

Implementation Code

#include<bits/stdc++.h>
using namespace std;
int main() {
  vector < int > vec = {
    10,
    20,
    30,
    40,
    50
  };

  vec.emplace(vec.begin() + 1, 15);
  vec.emplace(vec.begin() + 3, 25);
  for (int i = 0; i < vec.size(); i++) {
    cout << vec[i] << " ";
  }
  return 0;
}

Output

10 15 20 25 30 40 50
Time Complexity: O(n)
Space Complexity: O(1)

Using a Loop for Multiple Elements Insertions

In this approach, we use a loop to iterate through multiple elements and add them to the vector individually. This approach is mainly used for inserting multiple elements at different positions. This method is useful if we want to dynamically insert elements at different positions. This approach is more simple and scalable as it can handle multiple insertions dynamically.

Syntax

vector.insert(vector.begin() + position, value);
Where,
position is the index where the value is to be inserted.
value is the element to be inserted at a specific position

Implementation Code

#include<bits/stdc++.h>
using namespace std;
int main() {
  vector < int > vec = {
    10,
    20,
    30,
    40,
    50
  };
  vector < pair < int, int >> insertionvector = {{1,15},{3,25},{6,45}};
  for (auto & insertion: insertionvector) {
    vec.insert(vec.begin() + insertion.first, insertion.second);
  }
  for (int i = 0; i < vec.size(); i++) {
    cout << vec[i] << " ";
  }
  return 0;
}

Output

10 15 20 25 30 40 45 50
Time Complexity: O(n×k)
Space Complexity: O(1)
Updated on: 2024-12-24T13:22:09+05:30

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