vector apply for two-dimensional array

vector<vector<int> >f(m,vector<int>(n));//类似于a[m][n]

vector <vector <int>> f (m, vector <int> (n, 1)); // similar to a [m] [n] and the initial value of all 1

vector <int> f (m, 1); // apply a one-dimensional dynamic array

internal vector already contains new and delete operators, before use header file #include <vector>