How do I use iterators with 2D vectors in C++11?

Can you explain how to use iterators with 2D vectors in C++11?

Sure! In C++11, you can use iterators to traverse 2D vectors just like you would with 1D vectors. You can use nested loops.

Could you provide a code example?

Of course! Here's a simple example:

#include <iostream>
#include <vector>

int main() {
    std::vector<std::vector<int>> vec = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};
    for (auto it = vec.begin(); it != vec.end(); ++it) {
        for (auto jt = it->begin(); jt != it->end(); ++jt) {
            std::cout << *jt << " ";
        }
        std::cout << std::endl;
    }
}

This will print all the elements in the 2D vector.

What if I want to modify the elements while iterating?

You can use references in your iterator. Here's how:

for (auto& row : vec) {
    for (auto& elem : row) {
        elem *= 2; // Modify each element
    }
}

This will double each element in the 2D vector.

Thanks! Is there a way to use range-based for loops with 2D vectors?

Yes! You can use range-based for loops for a cleaner syntax:

for (const auto& row : vec) {
    for (const auto& elem : row) {
        std::cout << elem << " ";
    }
    std::cout << std::endl;
}

This is often more readable!