用队列实现栈（力扣第225题）

#include "stdio.h"
#include "stdbool.h"
#include "string.h"
#include "stdlib.h"
#include "assert.h"


//初始化队列
typedef int QueueDataType;

typedef struct queue {
	QueueDataType val;
	struct queue* next;
}Qnode;

typedef struct Queue {
	Qnode* phead;//队头
	Qnode* ptail;//队尾
	int size;//队列中的有效数据
}Queue;

//初始化队
void QueueInit(Queue* pq);

//入队
void QueuePush(Queue* pq,QueueDataType x);

//出队
void QueuePop(Queue* pq);

//获取队首元素
QueueDataType QueueFront(Queue* pq);

//获取队尾元素
QueueDataType QueueBack(Queue* pq);

//获取队列有效个数
int QueueSize(Queue* pq);

//判断队列是否为空，为空返回1，非空返回0
bool QueueEmpty(Queue* pq);

//打印队列
void QueuePrint(Queue* pq);

//销毁队列
void QueueDestory(Queue* pq);

#define _CRT_SECURE_NO_WARNINGS 1



//初始化队
void QueueInit(Queue* pq)
{
	assert(pq);
    pq->size=0;
    pq->phead=pq->ptail=NULL;
}

//入队
void QueuePush(Queue* pq, QueueDataType x)
{
	assert(pq);
    
	assert(pq);
	Qnode* newnode = (Qnode*)malloc(sizeof(Qnode));
	if (newnode == NULL)
	{
		printf("malloc fail\n");
		exit(-1);
	}
	pq->size++;
	newnode->val = x;
	newnode->next = NULL;
	if (pq->phead == NULL)
	{
		pq->phead = pq->ptail = newnode;
	}
	else
	{
		pq->ptail->next = newnode;
		pq->ptail = newnode;
	}
}

//出队
void QueuePop(Queue* pq) {
	assert(pq);
	Qnode* next = pq->phead->next;
	free(pq->phead);
	pq->size--;
	pq->phead = next;
}

//获取队首元素
QueueDataType QueueFront(Queue* pq) {
	assert(pq);
	assert(pq->size > 0);
	assert(pq->phead);
	return pq->phead->val;
}

//获取队尾元素
QueueDataType QueueBack(Queue* pq) {
	assert(pq);
	assert(pq->ptail);
	assert(pq->size > 0);
	return pq->ptail->val;
}

//获取队列有效个数
int QueueSize(Queue* pq) {
	assert(pq);
	return pq->size;
}

//判断队列是否为空，为空返回1，非空返回0
bool QueueEmpty(Queue* pq) {
	assert(pq);
	return pq->size == 0 ? 1 : 0;
}

//打印队列
void QueuePrint(Queue* pq) {
	assert(pq);
	assert(pq->phead);
	while (!QueueEmpty(pq))
	{
		printf("%d\n", pq->phead->val);
		QueuePop(pq);
	}
}

//销毁队列
void QueueDestory(Queue* pq) {
	assert(pq);
	Qnode* cur = pq->phead;
	while (cur) {
		Qnode* next = cur->next;
		free(cur);
		cur = next;
	}
	pq->phead = pq->ptail = NULL;
}

typedef struct {
    Queue pq1;
    Queue pq2;
    
} MyStack;


MyStack* myStackCreate() {
    MyStack* ST=(MyStack*)malloc(sizeof(MyStack));
    QueueInit(&ST->pq1);
    QueueInit(&ST->pq2);
    return ST;
}

void myStackPush(MyStack* obj, int x) {
    if(QueueEmpty(&obj->pq1))
    {
        QueuePush(&obj->pq2,x);
    }else{
         QueuePush(&obj->pq1,x);
    }
}

int myStackPop(MyStack* obj) {
    if(QueueEmpty(&obj->pq1)){
        while((&obj->pq2)->phead!=(&obj->pq2)->ptail)
        {
            QueuePush(&obj->pq1,QueueFront(&obj->pq2));
            QueuePop(&obj->pq2);
        }
        int vala=QueueFront(&obj->pq2);
         QueuePop(&obj->pq2);
        return vala;
    }
        if(QueueEmpty(&obj->pq2)){
        while((&obj->pq1)->phead!=(&obj->pq1)->ptail)
        {
            QueuePush(&obj->pq2,QueueFront(&obj->pq1));
            QueuePop(&obj->pq1);
        }
    }
    int valb=QueueFront(&obj->pq1);
    QueuePop(&obj->pq1);
     return valb;
}

int myStackTop(MyStack* obj) {
    if(QueueEmpty(&obj->pq1)){
        return (&obj->pq2)->ptail->val;
    }
     return (&obj->pq1)->ptail->val;
}

bool myStackEmpty(MyStack* obj) {
    if(QueueEmpty(&obj->pq1)&&QueueEmpty(&obj->pq2)){
        return true;
    }
    return false;
}

void myStackFree(MyStack* obj) {
    Qnode* cur1 = (&obj->pq1)->phead;
    while(cur1){
        Qnode* next=cur1->next;
        free(cur1);
        cur1=next;
    }
    (&obj->pq1)->phead=(&obj->pq1)->ptail=NULL;
    Qnode* cur2 = (&obj->pq2)->phead;
    while(cur2){
        Qnode* next=cur2->next;
        free(cur2);
        cur2=next;
    }
   (&obj->pq2)->phead=(&obj->pq2)->ptail=NULL;
      (&obj->pq2)->phead=(&obj->pq2)->ptail=NULL;
      free(obj);
      obj=NULL;
}

/**
 * Your MyStack struct will be instantiated and called as such:
 * MyStack* obj = myStackCreate();
 * myStackPush(obj, x);
 
 * int param_2 = myStackPop(obj);
 
 * int param_3 = myStackTop(obj);
 
 * bool param_4 = myStackEmpty(obj);
 
 * myStackFree(obj);
*/