how to create a vector of a certain size c++ code example

Example 1: c++ initialize a vector

#include <bits/stdc++.h> 
#include <vector> 
using namespace std; 
  
int main() 
{ 
// This vector initializes with the values: 10, 20, and 30
  vector<int> vect{ 10, 20, 30 }; 

    return 0; 
}

Example 2: c++ create vector of size

// create a vector with 20 integer elements
std::vector<int> arr(20);

for(int x = 0; x < 20; ++x)
   arr[x] = x;

Example 3: declare vector of size n in c++

#include <vector>

auto n = 20
// create a vector with n=20 integer elements
std::vector<int> arr(n);