psiepe_areece_doble_game/Startcode/stack.c

#include <stdlib.h>
#include "stack.h"

//TODO: grundlegende Stackfunktionen implementieren:
/*  * `push`: legt ein Element oben auf den Stack,
    * `pop`: entfernt das oberste Element,
    * `top`: liefert das oberste Element zurück,
    * `clearStack`: gibt den gesamten Speicher frei. */

// Pushes data as pointer onto the stack.
StackNode *push(StackNode *stack, void *data)
{
    StackNode *newItem = (StackNode*)calloc(1, sizeof(StackNode));
    if (newItem == NULL) return NULL;
    if (stack != NULL) {
        stack->left = newItem;
    }
    newItem->right = stack;
    newItem->left = NULL;
    newItem->data = data;

    return newItem;
}

// Deletes the top element of the stack (latest added element) and releases its memory. (Pointer to data has to be
// freed by caller.)
StackNode *pop(StackNode *stack)
{
    // grab next item, detatch it (becomes new head)
    StackNode *newHead = stack->right;
    newHead->left = NULL;

    // free the old head's struct
    free(stack);

    // give back the new head
    return newHead;
}

// Returns the data of the top element.
void *top(StackNode *stack)
{
    return stack->data;
    
}

// Clears stack and releases all memory.
void clearStack(StackNode *stack)
{
    do
    {
        stack = pop(stack);
    } while (stack != NULL);
}