stack

#include <stdio.h>
#include <stdlib.h>


typedef struct StackNode {
    int value;
    struct StackNode* prev;
 } StackNode;

typedef struct Stack {
   struct StackNode* top;
} Stack;


StackNode* NewStackNode(int value)
{
    /*creating StackNode*/
    StackNode* Node = malloc(sizeof(StackNode));
    Node -> value = value;
    Node -> prev = NULL;

    return Node;
}

Stack* NewStack(int value)
{
    /*creating StackNode*/
    StackNode* Node = NewStackNode(value);

    /*creating stack*/
    Stack* New = malloc(sizeof(Stack));
    New -> top = Node;

    return New;
}

void StackPush(Stack* s, int value)
{
    StackNode* Node = NewStackNode(value);

    Node -> prev = s-> top;
    s -> top = Node;
}

int StackPop(Stack* s)
{
    int output = -1;

    StackNode* freeNode;
    if(s->top){

        freeNode = s -> top;
        output = s->top->value;

        s -> top = s -> top -> prev;
        free(freeNode);
    }
    return output;
}

void StackRelease(Stack *s)
{
    while(s-> top){
        StackPop(s);
    }
    if(s)free(s);
}

int main(void)
{
    Stack* s = NewStack(6);
    int val;

    StackPush(s, 7);
    StackPush(s, 8);

    //StackRelease(s);

    val = StackPop(s);
    printf("%d\n", val);

    val = StackPop(s);
    printf("%d\n", val);

    val = StackPop(s);
    printf("%d\n", val);

    StackRelease(s);

    return 0;
}