如何将代码从指针更改为结构数组的指针？

Question

I have to change a 23000 lines code from pointers to pointers to struct arrays, the next code is an example, but if I solve the problem here that will be enough. I get the error: invalid type argument of unary '*' (have 'int'). If I write int *content that allows the code to run, but I have to write int=content and change the code *((ptab->content)+pC1+17) , I tried but I can't fix the error.

This is the example code in pointers to struct arrays

#include <iostream>
#include <cstdlib>
#include <ctime>
#include <conio.h>
#include <iomanip>
#include <stdio.h>
#include <Windows.h>

using namespace std;

struct box{
    int content;
};
struct box *ptab;

int pC1=5;

int main (){
    ptab=new struct box[64];

    if (*((ptab->content)+pC1+17)==0) {
        pC1=pC1+17;
    }
    cout<<pC1<<endl;
}

And this is the code in pointers, that already works.

#include <iostream>
#include <cstdlib>
#include <ctime>
#include <conio.h>
#include <iomanip>
#include <stdio.h>
#include <Windows.h>

using namespace std;

int *box;

int pC1=5;

int main (){
    box=new int[64];

    if (*(box+pC1+17)==0){
                                        pC1=pC1+17;
                                    }
    cout<<pC1<<endl;
}

Those are the examples, I would like to khow how to change from one code to the other, thanks.

Answer 1

In the bottom (working) code snippet, you're adding address offsets to an int pointer and dereferencing from that. That is, you're properly dereferencing a pointer.

In the top (nonfunctional) code snippet, you're adding address offsets to an int (not a pointer) and trying to dereference that, which isn't gonna work.

Answer 2

The code remains essentially the same. Pointer arithmetic works the same way regardless of the type. It's just that when you have the address of a struct, you need to specify which member you want with ->

#include <iostream>
using namespace std;

struct box{
    int content;
};
struct box *ptab;

int pC1=5;

int main (){
    ptab=new struct box[64];

    if ((ptab+pC1+17)->content==0) {  // you could also do (*(ptab+pC1+17)).content
        pC1=pC1+17;
    }
    cout<<pC1<<endl;
}