CODEWITHSUNDEEP
arraysclassc++11iteration
peedurrr
peedurrr

Reputation: 197

C++11 Multidimensional Array Iteration

To iterate through a C style multidimensional array we have 

int arr[3][4];

for (int row = 0; row < 3; row++){
    for (int col = 0; col < 4; col++){
        ...
    }
}

But how may one use iterators to iterate over the following:

array<array<int, 4>, 3> arr;

Using the following iterators?

array<array<int, 4>, 3>::iterator it1;

array<int, 4>::iterator it2;

Upvotes: 0

Views: 72

Answers (2)

Marandil
Marandil

Reputation: 1052

As usual:

array<array<int, 4>, 3> arr;
for(array<array<int, 4>, 3>::iterator it1 = arr.begin(); it1 != arr.end(); ++it1)
    for(array<int, 4>::iterator it2 = it1->begin(); it2 != it1->end(); ++it2)
        (*it2) = 0;

But it would be easier to use short c++11 range-based for loops

array<array<int, 4>, 3> arr;
for(auto &it1 : arr)
    for(auto &it2 : it1)
        it2 = 0;

Upvotes: 1

Angew is no longer proud of SO
Angew is no longer proud of SO

Reputation: 171127

If you need to use iterators, use them as usual:

for (auto itOuter = arr.begin(); itOuter != arr.end(); ++itOuter) {
  for (auto itInner = itOuter->begin(); itInner != itOuter->end(); ++itInner) {
    // use *itInner as appropriate
  }
}

You can just as well use range-based for loops, if they'd work for you:

for (auto &inner : arr) {
  for (int &elem : inner) {
    // use elem as appropriate
  }
}

Upvotes: 2

Related Questions