stack:FILO
操作:push 向棧頂壓入一個元素
pop 從棧頂彈出元素，pop一個空棧返回-1

節點結構體：

typedef struct _node
{
    int data;
    struct _node *next;
} Node;

棧結構體：

typedef struct linkedlist
{
    Node *head;
    Node *tail;
} Stack;

操作：

//初始化棧
void initializeStack(Stack *stack)
{
    stack->head = NULL;
    stack
 
->tail = NULL;
}

//向棧頂壓入元素
void push(Stack *stack, int data)
{
    Node *node = (Node *) malloc(sizeof(Node));
    node->data = data;
    if (stack->head == NULL)
    {
        stack->tail = node;
        node->next = NULL;
    }
    else
    {
        node->next = stack->head;
    }
    stack
 
->head = node;
}


//彈出棧頂元素並返回棧頂元素的值
int pop(Stack *stack)
{
    int data;
    Node *node = stack->head;
    if (stack->head == NULL)
    {
        data = -1;
    }
    else if (node == stack->tail)
    {
        data = stack->head->data;
        stack->head = stack->tail = NULL
 
;
        free(node);
    }
    else
    {
        data = stack->head->data;
        stack->head = stack->head->next;
        free(node);
    }

    return data;
}

//釋放所有未釋放的空間
void freeAll(Stack *stack)
{
    while(pop(stack)!=-1);
    printf("\nFree Complete!\n");
    return;
}

int main()
{
    Stack stack;
    initializeStack(&stack);
    push(&stack, 1);
    push(&stack, 2);
    push(&stack, 3);
    push(&stack, 4);
    push(&stack, 5);

    printf("%d ", pop(&stack));
    printf("%d \n", pop(&stack));  //5 4
    //1 2 3 <- top
    push(&stack, 11);
    push(&stack, 23);
    push(&stack, 323);  //1 2 3 11 23 323

    printf("%d ", pop(&stack));
    printf("%d ", pop(&stack));
    printf("%d ", pop(&stack));
    printf("%d ", pop(&stack));
    printf("%d ", pop(&stack));
    printf("%d ", pop(&stack));
    printf("%d \n", pop(&stack));

    freeAll(&stack);

    return 0;
}

小結：棧的實現基於連結串列，push操作相當於addHead