Checking for an Empty 2D Vector in Python

Python provides a simple way to check if a 2D list (which can be considered as a 2D vector) is empty. You can use the not operator to check if the list has any elements.

matrix = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
is_empty = not matrix
print(is_empty)  # False

empty_matrix = []
is_empty = not empty_matrix
print(is_empty)  # True

In the above example, the not operator is used to check if the matrix list is empty. If it yields True, it means the matrix is empty. In this case, it will print False because the matrix has elements. The same applies to the empty_matrix list, which is empty, so it will print True.

Checking for an Empty 2D Vector in C++

In C++, checking if a 2D vector is empty involves using the empty() function provided by the std::vector library. Here’s an example:

#include <iostream>
#include <vector>

int main() {
    std::vector<std::vector<int>> matrix = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};
    bool is_empty = matrix.empty();
    std::cout << std::boolalpha << is_empty << std::endl;  // false

    std::vector<std::vector<int>> empty_matrix;
    is_empty = empty_matrix.empty();
    std::cout << std::boolalpha << is_empty << std::endl;  // true

    return 0;
}

In the C++ example, the empty() function is used to check if matrix and empty_matrix are empty or not. The function returns true if the vector is empty and false otherwise. By using std::boolalpha with std::cout, we print true and false instead of 1 and 0, respectively.

Conclusion

By using the appropriate methods provided by your programming language, you can easily check if a 2D vector is empty. In Python, you can utilize the not operator, while in C++, you can use the empty() function.