// Create an empty vector
vector<int> vect;
// Create a vector of size n with all values as 10.
vector<int> vect(n, 10);
//initilize with values
vector<int> vect{ 10, 20, 30 };
//initilize with old array
vector<int> vect(arr, arr + n);
//initilize with old vector
vector<int> vect2(vect1.begin(), vect1.end());