C++ How to dynamically create a 2D vector

Question

I\'m trying to create an n x n vector that I can later cout as a table/matrix. Xcode points to the = in the for loop and tells me No

Answer 1

When the constructor of row is called, all elements are initialized too. I think this code does what you're looking to do:

for (int i=0; i<n; i++) {
    row[i].resize(n);
}

Now all elements of row will be of size n.

Answer 2

Try the following

int n = 5;
std::vector< std::vector<int> > row(n);
for (int i=0; i<n; i++) {
   row[i].push_back( std::vector<int>(n) );
}

or

int n = 5;
std::vector< std::vector<int> > row(n, std::vector<int>( n ) );

Answer 3

The simple solution is to use the relevant constructor of std::vector, initializing it to n elements each having the value of val - no loops necessary.

std::vector<T> (n, val);

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Having your original snippet we would end up with the following, which will initialize row to have n std::vectors, each of which having n elements.

std::vector<std::vector<int> > row (n, std::vector<int> (n));