从 pop 函数返回错误的地址 [英] returning wrong address from pop function
问题描述
在解决了我的结构的其他问题后,我的推送按预期工作,但是我的弹出返回错误的地址,我不知道为什么 -
After solving other issues with my struct, my push works as intended however my pop returns the wrong address and I'm not sure why -
QNode* const Q_Pop(Q* const pointerQ){
... // empty check
QNode* tempNode = pointerQ->front.next;
pointerQ->front.next = (tempNode->next);
tempNode->next->prev = &(pointerQ->front);
return tempNode;
}
我相当确定我实际删除和重新链接堆栈的逻辑是正确的,但我对指针的使用和返回它们是一团糟.
I'm fairly certain my logic for the actual removal and relinking of the stack is correct but my use of pointers and returning them is messed up.
结构 -
struct QueueNode {
struct QueueNode *prev; /* Previous list element. */
struct QueueNode *next; /* Next list element. */
};
typedef struct QueueNode QNode;
struct Queue {
QNode front; // sentinel node at the front of the queue
QNode rear; // sentinel node at the tail of the queue
};
typedef struct Queue Q;
感谢您的帮助!
推荐答案
你不应该使用哨兵节点";这是没有意义的,而且非常令人困惑.队列可以简单地表示为第一个元素的 QNode*
.它总是指向第一个元素;如果为NULL
,则队列为空;如果 element->next
是 NULL
,它是最后一个元素,因为没有下一个.使用它非常简单.
You shouldn't be using "sentinel nodes"; this is pointless and very confusing. A queue can be simply represented as a QNode*
to the first element. It always points to the first element; if it's NULL
, the queue is empty; if element->next
is NULL
, it's the last element because there isn't a next one. It's very simple to work with that.
struct QueueNode {
// stuff
// stuff
// stuff
struct QueueNode* prev; // this may be optional
struct QueueNode* next;
};
typedef struct QueueNode QNode;
void push_front(QNode** queue, QNode* pushme) {
pushme->prev = NULL;
pushme->next = *queue;
(*queue)->prev = pushme;
*queue = pushme;
}
void push_end(QNode** queue, QNode* pushme) {
QNode* node = *queue;
if (node) {
while (node->next) node = node->next;
node->next = pushme;
pushme->prev = node;
pushme->next = NULL;
}
else {
*queue = pushme;
(*queue)->next = (*queue)->prev = NULL;
}
}
QNode* pop_front(QNode** queue) {
QNode* node = *queue;
if (node)
*queue = node->next;
return node;
}
QNode* pop_end(QNode** queue) {
QNode* node = *queue;
if (node) {
while (node->next) node = node->next;
if (node->prev) {
node->prev->next = NULL;
node->prev = NULL;
}
else
*queue = NULL;
}
return node;
}
QNode* create_node_front(QNode** queue) {
QNode* node = malloc(sizeof(QNode));
push_front(queue, node);
return node;
}
QNode* create_node_end(QNode** queue) {
QNode* node = malloc(sizeof(QNode));
push_end(queue, node);
return node;
}
QNode* my_queue = NULL; // declare an empty queue
QNode* my_node = create_node_end(&my_queue); // create a new node, its already stored in the queue
我没有测试它,但它给出了一个大致的想法.
I didn't test it, but it gives a general idea.
您可以使用 push_front()
或 create_node_front()
推送(无循环,最佳性能)然后使用 pop_end()
弹出队列效果(FIFO),或使用 pop_front()
弹出具有堆栈效应(LIFO).
You can push with push_front()
or create_node_front()
(no loops, best performance) then pop with pop_end()
to have a queue effect (FIFO), or pop with pop_front()
to have a stack effect (LIFO).
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