Question

So, I completed a project with ease in C++, only to realize I was supposed to write it in Java. This wouldn’t be too big of a deal, except that my code uses multidimensional vectors, like:

vector <vector<int> > arr  

Is there something equivalent in Java that would give the same result without having to drastically rewrite the program?

Here’s the code snippet from the C++ program that I am having trouble translating:

vector <vector <int> > arr;

cin >> n;

while (n > 0)
{
    vector <int> row;
    int u;

    for (int i = 0; i < n ; ++i)
    {
        cin >> u;
        row.push_back(u);
    }

    arr.push_back(row);

    n = comb(row.size(), k);
    k++;
}

for (int i = 0; i < arr.size(); i+=2)
    for (int j = 0; j < arr[i].size(); ++j)
        sum += arr[i][j];

for (int i = 1; i < arr.size(); i+=2)
    for (int j = 0; j < arr[i].size(); ++j)
        diff += arr[i][j];

Answer 1

The ArrayList should provide the functionality that you need, if you declare it as an ArrayList<ArrayList<Integer>>. Your calls to push_back() are equivalent to calls to add(). You will lose the array index access notation, but this can be resolved by chaining calls to get().