How to correctly use pointers in code - c++

Question

For the following code, how can I find [A^-1] using pointers(equation for [A^-1]= 1/ det (A)? I am not sure whether pointers are used in the arithmetic or if they are used to call a value. Explaining what a pointer would be nice as I'm not exactly sure what they even do. I have most of the code written, except for this one part, so any help is much appreciated. Thanks in advance.
#include <iostream>
#include <cmath>
#include <string>
#include <fstream>
#include <ctime>
#include <cstdlib>
#include <bits/stdc++.h>
#define N 3
using namespace std;
template<class T>
void display(T A[N][N])
{
for (int i=0; i<N; i++)
{
for (int j=0; j<N; j++)
cout << A[i][j] << "\t\t";
cout << endl;
}
}
template<class T>
void display(T A[N])
{
for (int i=0; i<N; i++)
{
cout << A[i]<< "\n";
}
}
void getCofactor(int A[N][N], int temp[N][N], int p, int q, int n)
{
int i = 0, j = 0;
for (int row = 0; row < n; row++)
{
for (int col = 0; col < n; col++)
{
if (row != p && col != q)
{
temp[i][j++] = A[row][col];
if (j == n - 1)
{
j = 0;
i++;
}
}
}
}
}
int determinant(int A[N][N], int n)
{
int D = 0;
if (n == 1)
return A[0][0];
int temp[N][N];
int sign = 1;
for (int f = 0; f < n; f++)
{
getCofactor(A, temp, 0, f, n);
D += sign * A[0][f] * determinant(temp, n - 1);
sign = -sign;
}
return D;
}
void adjoint(int A[N][N],int adj[N][N])
{
if (N == 1)
{
adj[0][0] = 1;
return;
}
int sign = 1, temp[N][N];
for (int i=0; i<N; i++)
{
for (int j=0; j<N; j++)
{
getCofactor(A, temp, i, j, N);
sign = ((i+j)%2==0)? 1: -1;
adj[j][i] = (sign)*(determinant(temp, N-1));
}
}
}
bool inverse(int A[N][N]){
int det = determinant(A, N);
if (det == 0){
cout << "Singular matrix, can't find its inverse";
return false;
}
return true;
}
void computeInverse(int A[N][N], float inverse[N][N]){
int det = determinant(A, N);
int adj[N][N];
adjoint(A, adj);
for (int i=0; i<N; i++)
for (int j=0; j<N; j++)
inverse[i][j] = adj[i][j]/float(det);
cout<<"\nThe Inverse of the Matrix A is:"<<endl;
display(inverse);
}
int main()
{
system("cls");
int A[N][N] = {{-1, 4, -2}, {-3, -2, +1}, {+2, -5, +3}};
char X[N];
int B[N];
float inv[N][N];
cout<<"\nEnter a 3*3 Matrix A"<<endl;
for(int i=0;i<N;i++){
for(int j=0;j<N;j++){
cin>>A[i][j];
}
}
cout<<"\nEnter variables x, y, z for Matrix X"<<endl;
for(int i=0;i<N;i++){
cin>>X[i];
}
if (X[0] == 'x' && X[1] == 'y' && X[2] == 'z')
cout<<"\nMatrix X is Valid"<<endl;
else{
cout<<"\nMatrix X is Invalid"<<endl;
return -1;
}
cout<<"\nEnter values for Matrix B"<<endl;
for(int i=0; i<N; i++)
cin>>B[i];
cout<<"\nMatrix A is:------->\n";
display(A);
cout<<"\nMatrix X is:------->\n";
display(X);
cout<<"\nMatrix B is:------->\n";
display(B);
bool isInverseExist = inverse(A);
if (isInverseExist)
computeInverse(A, inv);
return 0;
}

Answer 1

Okay, Here is a simple pointer example using a char array. This can work with other data types as well. Don't remember where I read it; Think of a pointer as an empty bottle.
lets break this down in English first then I'll share a simple example that can be compiled. Imagine that you have 10 m&m's sitting in front of you on a table.
These m&m's represent a character array that we will call char mm[10]; Assume that this array is filled with chars that represent the color of all 10 of the m&m's
Now, we don't want to leave our candy's on the table all day so we will store all ten of the m&m's in a special jar specifically made for the m&m's. this jar will be called char* mm_ptr;
So now we are left with a table of m&m's and a jar sitting next to the pile. The next step is to fill the jar with the m&m's and you do it like this: mm_ptr = mm;
You now have a "jar full of m&m's". This allows you to access the m&m's directly from the jar!
Here is a Working example of of putting m&m's into a jar:
#include <iostream>
//using namespace std;
int main(){//The main function is our table
char mm[10]; //Our pile of m&m's
for(int i=0; i<10; i++){
if(i < 5){
mm[i] = 'b'; //Lets say that half of the m&m's are blue
}else{
mm[i] = 'r'; //and that the other half is red
}
}
char* mm_ptr; //This is our bottle that we will
//use to store our m&m's
mm_ptr = mm; //this is us storing the m&m's in the jar!
for(int i=0; i<10; i++){//Lets dump those candies back onto the table!
std::cout<<mm_ptr[i]<<std::endl;
}
return 0;
}
A correctly initialized pointer will work almost exactly like a normal array