declaring vector c++

// CPP program to initialize a vector from 
// an array. 
#include <bits/stdc++.h> 
using namespace std; 
  
int main() 
{ 
    int arr[] = { 10, 20, 30 }; 
    int n = sizeof(arr) / sizeof(arr[0]); 
  
    vector<int> vect(arr, arr + n); 
  
    for (int x : vect) 
        cout << x << " "; 
  
    return 0; 
} 
// CPP program to create an empty vector 
// and push values one by one. 
#include <bits/stdc++.h> 
using namespace std; 
  
int main() 
{ 
    int n = 3; 
  
    // Create a vector of size n with 
    // all values as 10. 
    vector<int> vect(n, 10); 
  
    for (int x : vect) 
        cout << x << " "; 
  
    return 0; 
} 
// CPP program to create an empty vector 
// and push values one by one. 
#include <vector>

using namespace std;
int main() 
{ 
    // Create an empty vector 
    vector<int> vect;  
    //add/push an integer to the end of the vector
    vect.push_back(10); 
	//to traverse and print the vector from start to finish
    for (int x : vect) 
        cout << x << " ";

    return 0; 
}// CPP program to initialize a vector from 
// another vector. 
#include <bits/stdc++.h> 
using namespace std; 
  
int main() 
{ 
    vector<int> vect1{ 10, 20, 30 }; 
  
    vector<int> vect2(vect1.begin(), vect1.end()); 
  
    for (int x : vect2) 
        cout << x << " "; 
  
    return 0; 
} 
// CPP program to initialize a vector like 
// an array. 
#include <bits/stdc++.h> 
using namespace std; 
  
int main() 
{ 
    vector<int> vect{ 10, 20, 30 }; 
  
    for (int x : vect) 
        cout << x << " "; 
  
    return 0; 
} 
// CPP program to create an empty vector 
// and push values one by one. 
#include <bits/stdc++.h> 
using namespace std; 
  
int main() 
{ 
    // Create an empty vector 
    vector<int> vect;  
     
    vect.push_back(10); 
    vect.push_back(20); 
    vect.push_back(30); 
  
    for (int x : vect) 
        cout << x << " "; 
  
    return 0; 
}