size of a matrix using vector c++

To find the size of a matrix using vectors in C++, you can follow these steps:

1. First, include the necessary header file for using vectors: cpp #include <vector>

2. Declare a 2D vector to represent the matrix. Specify the number of rows and columns in the matrix: cpp std::vector<std::vector<int>> matrix; Note: You can replace int with the desired data type of the matrix elements.

3. Read the input matrix from the user and populate the vector. You can use nested loops to iterate over the rows and columns of the matrix and store the elements in the vector: ```cpp int rows, cols; std::cout << "Enter the number of rows: "; std::cin >> rows; std::cout << "Enter the number of columns: "; std::cin >> cols;

matrix.resize(rows, std::vector(cols));

std::cout << "Enter the elements of the matrix:\n"; for (int i = 0; i < rows; i++) { for (int j = 0; j < cols; j++) { std::cin >> matrix[i][j]; } } ```

1. To get the size of the matrix, you can use the size() function provided by the vector class. The size() function returns the number of elements in the vector, which in this case represents the number of rows in the matrix: cpp int size = matrix.size();

2. You can also get the number of columns in the matrix by accessing the size of any row vector in the matrix. Since all rows have the same number of columns, accessing the size of any row will give you the number of columns: cpp int numCols = matrix[0].size();

3. Finally, you can print the size of the matrix and the number of rows and columns: cpp std::cout << "Size of the matrix: " << size << std::endl; std::cout << "Number of rows: " << size << std::endl; std::cout << "Number of columns: " << numCols << std::endl;

Here's the complete code example:

#include <iostream>
#include <vector>

int main() {
    std::vector<std::vector<int>> matrix;
    int rows, cols;
    std::cout << "Enter the number of rows: ";
    std::cin >> rows;
    std::cout << "Enter the number of columns: ";
    std::cin >> cols;

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

    std::cout << "Enter the elements of the matrix:\n";
    for (int i = 0; i < rows; i++) {
        for (int j = 0; j < cols; j++) {
            std::cin >> matrix[i][j];
        }
    }

    int size = matrix.size();
    int numCols = matrix[0].size();

    std::cout << "Size of the matrix: " << size << std::endl;
    std::cout << "Number of rows: " << size << std::endl;
    std::cout << "Number of columns: " << numCols << std::endl;

    return 0;
}

This code will prompt the user to enter the number of rows and columns for the matrix, followed by the elements of the matrix. It then calculates and prints the size of the matrix (number of rows) and the number of columns.