Check out example codes for "inserting at start in vector c++". It will help you in understanding the concepts better.

Code Example 1

// inserting into a vector
#include <iostream>
#include <vector>

int main ()
{
  std::vector<int> myvector (3,100);
  std::vector<int>::iterator it;

  it = myvector.begin();
  it = myvector.insert ( it , 200 );

  myvector.insert (it,2,300);

  // "it" no longer valid, get a new one:
  it = myvector.begin();

  std::vector<int> anothervector (2,400);
  myvector.insert (it+2,anothervector.begin(),anothervector.end());

  int myarray [] = { 501,502,503 };
  myvector.insert (myvector.begin(), myarray, myarray+3);

  std::cout << "myvector contains:";
  for (it=myvector.begin(); it<myvector.end(); it++)
    std::cout << ' ' << *it;
  std::cout << '\n';

  return 0;
}

Code Example 2

std::vector<int> v;
v.push_back(10);

Code Example 3

// Inserting at start
vector_name.insert(vector_name.begin(), element_to_be_inserted);

// Inserting after xth element
vector_name.insert(vector_name.begin()+(x-1), element_to_be_inserted);

// Inserting at last
vector_name.push_back(element_to_be_inserted);

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