how to declare two d matrix in c++

#include <iostream>
#include <vector>

int main() {
    int rows = 3; // Number of rows
    int cols = 4; // Number of columns

    std::vector<std::vector<int>> matrix(rows, std::vector<int>(cols));

    return 0;
}

Explanation: - #include <iostream>: Includes the input/output stream library. - #include <vector>: Includes the vector library for using vectors in C++. - int main() { ... }: The main function where the program execution begins.

Within main(): - int rows = 3;: Declares an integer variable rows and assigns it the value 3, representing the number of rows in the matrix. - int cols = 4;: Declares an integer variable cols and assigns it the value 4, representing the number of columns in the matrix. - std::vector<std::vector<int>> matrix(rows, std::vector<int>(cols));: - Declares a 2D matrix named matrix. - std::vector<int>(cols) creates a vector with cols number of integers (representing a row). - std::vector<std::vector<int>> matrix(rows, ...); creates rows number of such rows, forming a 2D matrix structure.

The resulting matrix will have 3 rows and 4 columns, initialized with default integer values (which are zeros for int type).