vector<int> vect{ 10, 20, 30 };

int n = 3;

// Create a vector of size n with
// all values as 10.
vector<int> vect(n, 10);

// Create an empty vector
    vector<int> vect; 

    vect.push_back(10);
    vect.push_back(20);
    vect.push_back(30);

int arr[] = { 10, 20, 30 };
int n = sizeof(arr) / sizeof(arr[0]);

vector<int> vect(arr, arr + n);

vector<int> vect1{ 10, 20, 30 };
vector<int> vect2(vect1.begin(), vect.end());