Put more values onto the end of the vector,it will grow as needed : vector size « vector « C++ Tutorial

1. C++ Tutorial
2. vector
3. vector size

#include <iostream>
#include <vector>
#include <cctype>
using namespace std;
   
int main()
{
  vector<char> v(10); // create a vector of length 10
  unsigned int i;
   
  // display original size of v
  cout << "Size = " << v.size() << endl;
   
  // assign the elements of the vector some values
  for(i=0; i<10; i++) v[i] = i + 'a';
   
  // display contents of vector
  cout << "Current Contents:\n";
  for(i=0; i<v.size(); i++) cout << v[i] << " ";
  cout << "\n\n";
   
  cout << "Expanding vector\n";
  
  for(i=0; i<10; i++) v.push_back(i + 10 + 'a');
   
  // display current size of v
  cout << "Size now = " << v.size() << endl;
   
  // display contents of vector
  cout << "Current contents:\n";
  for(i=0; i<v.size(); i++) cout << v[i] << " ";
  cout << "\n\n";
   
  // change contents of vector
  for(i=0; i<v.size(); i++) v[i] = toupper(v[i]);
  cout << "Modified Contents:\n";
  for(i=0; i<v.size(); i++) cout << v[i] << " ";
  cout << endl;
   
  return 0;
}