Using a struct inside a struct Stack. What is wrong?

Question

I'm trying to use a struct inside a struct Stack. The Point struct stores two members, and I want to know how to reorganize this code without using a vector or pair.

typedef struct {
    // Array to store stack elements
    int arr[MAX_SIZE];
    // Index of the top element in the stack
    int top;

    struct Point {

        int x;
        int y;
    } point;


} Stack;

Does anyone know where to start?

I'm trying to create a set of pairs with a struct (x, y). I'm working on a maze algorithm. Trying to figure out how to set up this struct/struct stack to create ordered pairs for pushing and popping.

Answer 1

A stack is just a structure to store a list of some thing. It can be any thing.

Physically, I can stack a bunch of plates. Or papers. Or books. Or boxes, where each box holds two teddy bears.

Same in code. Each item in a stack can be a integer, or a string, or a Student or Employee or... a point. Hence, you can create a thing:

typedef
struct Point
{
    int x, y;
}
Point;

And you can create a stack that holds that kind of thing:

typedef
struct Stack
{
    Point arr[MAX_STACK_SIZE];
    int top; // -1 for empty stack
}
Stack;

Thereafter it is easy to create/initialize a stack:

void CreateStack( Stack * S )
{
    S.top = -1;
}

And push a point:

void Push( Stack * S, Point p )
{
    if (S.top + 1 < MAX_STACK_SIZE)
        S.arr[++S.top] = p;
}

etc. User code then becomes very easy:

int main(void)
{
    Stack my_stack;
    CreateStack( &my_stack );

    Point p = { 2, 3 };
    Push( &my_stack, p );

    ...

P.S. You can make a function to create a point, too:

Point CreatePoint( int x, int y )
{
    Point p = { x, y };
    return p;
}

And then use it:

    Push( &my_stack, CreatePoint( 5, 7 ) );