Home » C++ STL

Erasing Elements from a Vector in C++

C++ STL vector::erase() Example: Here, we are going to learn how to erase elements in C++ Vector.
Submitted by Vivek Kothari, on November 07, 2018

Erasing Elements from a Vector

Vectors are sequence container and work like dynamic arrays. Vectors stores elements in contiguous memory locations i.e in a linear sequence. vector::erase() is an inbuilt function in c++ used for removing the specific element from vector or removing the range of elements.

Syntax

VectorName.erase (pos);
VectorName.erase(StartPos, EndPos);

Here, VectorName is the name of vector used at the time of declaration.

Parameters

• Pos: It is the position of an element of the vector you want to delete denoted by the iterator.
• StartPos: It is the iterator specifying a start of the range to be removed.
• EndPos: It is the iterator pointing to one position ahead of the last element to be removed from the range.

Note: erase(StartPos, EndPos) specifies the range which includes all the elements between StartPosand EndPos, including the element pointed by StartPosbut not include the one pointed by EndPosi. e [StartPos, EndPos).

Example 1

This example shows the basic working of vector::erase() function:

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

int main() {
  std::vector<int> MyVector;

  // insert into vector
  for (int i = 1; i <= 8; i++) MyVector.push_back(i);
  cout << " After elements insertion : ";
  for (unsigned i = 0; i < MyVector.size(); ++i) cout << ' ' << MyVector[i];

  cout << endl;

  // erase the 3rd element
  MyVector.erase(MyVector.begin() + 3);
  cout << " After removing 3rd element: ";
  for (unsigned i = 0; i < MyVector.size(); ++i) cout << ' ' << MyVector[i];

  cout << endl;

  // erase the first 3 elements:
  MyVector.erase(MyVector.begin(), MyVector.begin() + 3);
  cout << " After removing first three elements: ";
  for (unsigned i = 0; i < MyVector.size(); ++i) cout << ' ' << MyVector[i];

  return 0;
}

Output

 After elements insertion :  1 2 3 4 5 6 7 8
 After removing 3rd element:  1 2 3 5 6 7 8
 After removing first three elements:  5 6 7 8
 

Example 2

Erase all even numbers in a vector.

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

int main() {
  vector<int> c;

  // inserting in vector
  for (int i = 1; i <= 10; i++) c.push_back(i);

  cout << "Elements in Vector : ";
  for (int i = 0; i <= 9; i++) {
    cout << c[i] << " ";
  }
  cout << endl;

  // Erase all even numbers
  for (vector<int>::iterator it = c.begin(); it != c.end();) {
    // if number is even remove it
    if (*it % 2 == 0) {
      it = c.erase(it);
    } else {
      // if number if not even check for next element
      ++it;
    }
  }
  cout << "After removing all even numbers : ";
  for (vector<int>::iterator it = c.begin(); it != c.end(); it++) {
    cout << *it << " ";
  }
  return 0;
}

Output

Elements in Vector : 1 2 3 4 5 6 7 8 9 10
After removing all even numbers : 1 3 5 7 9