Freeing a jagged array in C++ - c++

Question

#include <iostream>
#include <stdlib.h>
using namespace std;
float **div(float **A, float **B, int row, int column) {
float **D;
D = new float *[row];
// D= ( float **)malloc(sizeof(float *) * row);
for (int x = 0; x < row; x++) {
D[x] = new float[column];
// D[x] = (float (*))malloc(sizeof(float) * column);
for (int y = 0; y < column; y++) {
D[x][y] = (A[x][y] / B[x][y]);
}
}
return D;
}
int main() {
int x = 0, y = 0, row = 20, column = 5;
float **N;
// N =(float **)malloc(sizeof(float *) * row);
N = new float *[row];
for (x = 0; x < row; x++) {
N[x] = new float[column];
// N[x]=(float*)malloc(row*column*sizeof(float));
for (y = 0; y < (column); y++) {
N[x][y] = 1;
}
}
N = div(N, N, row, column);
cout << "Displaying N ..." << endl;
for (int x = 0; x < 10; x++) {
for (int y = 0; y < 5; y++) {
cout << N[x][y] << " ";
}
cout << endl;
}
for (int x = 0; x < 20; x++) {
delete[] N[x];
}
delete[] N;
return 0;
}
I am trying to free the all the memory, but it is freed the memory which I declared in main, but the function div also occupying the same memory of size input array N and it is not freed. Is there any way to delete the memory which is occupied the function.

Answer 1

Please look at here, my example of new and delete a int[m][n], I hope this can help you:
int main()
{
//a[m][n]
const int m = 5, n=6;
int **p = new int*[m];
for(int i=0; i<m; ++i)
p[i] = new int[n];
for(int i=0; i<m; ++i)
delete[] p[i]; //delete array
delete[] p;
p = nullptr;
}

Answer 2

Using std::array would remove memory management:
template <std::size_t ROW, std::size_t COL>
using Matrix = std::array<std::array<float, COL>, ROW>;
template <std::size_t ROW, std::size_t COL>
Matrix<ROW, COL> div(const Matrix<ROW, COL>& A, const Matrix<ROW, COL>& B)
{
Matrix<ROW, COL> res;
for (std::size_t x = 0; x != ROW; ++x) {
for (std::size_t y = 0; y != COL; ++y) {
res[x][y] = (A[x][y]/B[x][y]);
}
}
return res;
}
template <std::size_t ROW, std::size_t COL>
void display(const Matrix<ROW, COL>& m)
{
for (std::size_t x = 0; x != ROW; ++x) {
for (std::size_t y = 0; y != COL; ++y) {
std::cout << m[x][y] << " ";
}
std::cout << std::endl;
}
}
int main()
{
Matrix<20, 5> N;
for (std::size_t x = 0; x != 20; ++x) {
for (std::size_t y = 0; y != 5; ++y) {
N[x][y] = 1;
}
}
N = div(N, N);
std::cout << "Displaying N ..." << std::endl;
display(N);
}
Demo