请你仅使用两个队列实现一个后入先出(LIFO)的栈,并支持普通栈的全部四种操作(push、top、pop 和 empty)
参考代码:
typedef struct {
Queue q1;
Queue q2;
} MyStack;
MyStack* myStackCreate() {
MyStack*st=(MyStack*)malloc(sizeof(MyStack));
QueueInit(&st->q1);
QueueInit(&st->q2);
return st;
}
void myStackPush(MyStack* obj, int x) {
//入栈时入空队列
if(!QueueEmpty(&obj->q1))
{
QueuePush(&obj->q1,x);
}
else
{
QueuePush(&obj->q2,x);
}
}
int myStackPop(MyStack* obj) {
//出栈时,先将有数据的队列出队到最后一个元素,并将数据入队到空队列,最后将最后一个数据出队达到出栈的效果
Queue* emptyQ=&obj->q1;
Queue* noemptyQ=&obj->q2;
if(QueueEmpty(&obj->q2))
{
emptyQ=&obj->q2;
noemptyQ=&obj->q1;
}
while(QueueSize(noemptyQ)>1)
{
QueuePush(emptyQ,QueueFront(noemptyQ));
QueuePop(noemptyQ);
}
int top=QueueFront(noemptyQ);
QueuePop(noemptyQ);
return top;
}
int myStackTop(MyStack* obj) {
if(!QueueEmpty(&obj->q1))
{
return QueueBack(&obj->q1);
}
else
{
return QueueBack(&obj->q2);
}
}
bool myStackEmpty(MyStack* obj) {
return QueueEmpty(&obj->q1)&&QueueEmpty(&obj->q2);
}
void myStackFree(MyStack* obj) {
QueueDestroy(&obj->q1);
QueueDestroy(&obj->q1);
free(obj);
}
typedef int QDataType;
typedef struct QueueNode
{
struct QueueNode* next;
QDataType data;
}QueueNode;
typedef struct Queue
{
QueueNode* head;
QueueNode* tail;
// size_t _size;
}Queue;
//void QueueInit(QueueNode** pphead, QueueNode** pptail);
void QueueInit(Queue* pq);
void QueueDestroy(Queue* pq);
void QueuePush(Queue* pq, QDataType x);
void QueuePop(Queue* pq);
QDataType QueueFront(Queue* pq);
QDataType QueueBack(Queue* pq);
int QueueSize(Queue* pq);
bool QueueEmpty(Queue* pq);
void QueueInit(Queue* pq)
{
assert(pq);
pq->head = NULL;
pq->tail = NULL;
}
void QueueDestroy(Queue* pq)
{
assert(pq);
QueueNode* cur = pq->head;
while (cur != NULL)
{
QueueNode* next = cur->next;
free(cur);
cur = next;
}
pq->head = pq->tail = NULL;
}
void QueuePush(Queue* pq, QDataType x)
{
assert(pq);
QueueNode* newnode = (QueueNode*)malloc(sizeof(QueueNode));
newnode->data = x;
newnode->next = NULL;
if (pq->head == NULL)
{
pq->head = pq->tail = newnode;
}
else
{
pq->tail->next = newnode;
pq->tail = newnode;
}
}
void QueuePop(Queue* pq)
{
assert(pq);
//if (pq->head == NULL)
// return;
assert(!QueueEmpty(pq));
QueueNode* next = pq->head->next;
free(pq->head);
pq->head = next;
if (pq->head == NULL)
{
pq->tail = NULL;
}
}
QDataType QueueFront(Queue* pq)
{
assert(pq);
assert(!QueueEmpty(pq));
return pq->head->data;
}
QDataType QueueBack(Queue* pq)
{
assert(pq);
assert(!QueueEmpty(pq));
return pq->tail->data;
}
int QueueSize(Queue* pq)
{
assert(pq);
int n = 0;
QueueNode* cur = pq->head;
while (cur)
{
++n;
cur = cur->next;
}
return n;
}
bool QueueEmpty(Queue* pq)
{
assert(pq);
return pq->head == NULL;
}