How can I iterate through a 2D vector in C++11?

How can I iterate through a 2D vector in C++11?

You can use nested loops to iterate through a 2D vector in C++11. Here's an example:

#include <vector>
#include <iostream>

int main() {
    std::vector<std::vector<int>> vec = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};
    for (size_t i = 0; i < vec.size(); ++i) {
        for (size_t j = 0; j < vec[i].size(); ++j) {
            std::cout << vec[i][j] << " ";
        }
        std::cout << std::endl;
    }
    return 0;
}

What if I want to access elements using range-based for loops?

You can use range-based for loops for a more concise syntax. Here's how:

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

Can you explain how the auto keyword works in this context?

The auto keyword automatically deduces the type of the variable. In the range-based for loop, auto& allows you to iterate over each element without explicitly specifying the type, making the code cleaner.

Are there any performance considerations I should be aware of?

Yes, using auto& avoids unnecessary copies of the elements, which can improve performance, especially for large data types. However, if you don't need to modify the elements, you can use const auto& to ensure they remain unchanged.