initialize dynamic array elements to zeros

Question

For a fixed array,

  // will initialize the missing elements to 0 as well
   A[max_row][max_col] = {0,}

Can we achieve this in dynamic arrays (multidimensional, in particular)?

Side question: if we can't, and we are forced to use nested loop, then how does the initialization time of the trick above compared to nested loop initialization?

I don't want to vector, otherwise this question is meaningless. Thanks for the advise :)

I know you can do that. Everyone wants to use vector, but I don't want to. I am sorry I forgot to include that. Thanks though. — CppLearner
– CppLearner, Commented Nov 27, 2011 at 5:14
Regarding your first question: What happened when you tried? Regarding your second question: Internally C++ represents a multi-dimensional array as a single flat list of memory locations of type "whatever" (where whatever is how you invoked new). You don't need a nested for loop if you do it that way. You can just use a pointer to run through row x col number of positions with a single loop. — DavidO
– DavidO, Commented Nov 27, 2011 at 5:17
Why don't you want to? Just for understanding (practice), or for real use? — GManNickG
– GManNickG, Commented Nov 27, 2011 at 5:18
Exact Duplicate of How do you initialise a dynamic array in C++? — Alok Save
– Alok Save, Commented Nov 27, 2011 at 5:20
@CppLearner: No. The overhead of a std::vector (if it even exists at all, which I believe it doesn't) is absolutely trumped by the gains in maintainability and program correctness. — GManNickG
– GManNickG, Commented Nov 27, 2011 at 5:27

GManNickG · Accepted Answer · 2011-11-27 05:19:37Z

12

If you do this: new int[N]() /* note parenthesis */, then they are all zero initialized.

You should really use a std::vector, though.

answered Nov 27, 2011 at 5:19

GManNickG

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