1. 题目描述

2. 思路分析

用两个栈实现，一个栈进行入队操作，另一个栈进行出队操作。
出队操作：当出队的栈不为空时，直接进行出栈操作；如果为空，需要把入队的栈元素全部导入到出队的栈，然后再进行出栈操作

3. 代码实现

typedef int STDataType;
#define INIT_CAPACITY 4
typedef struct Stack
{STDataType* a;int top;  //栈顶int capacity;  //容量
}ST;//初始化栈
void STInit(ST* ps);
//入栈
void STPush(ST* ps, STDataType x);
//出栈
void STPop(ST* ps);
//获取栈顶元素
STDataType STTop(ST* ps);
//获取栈中有效元素个数
int STSize(ST* ps);
//检测栈是否为空
bool STEmpty(ST* ps);
//销毁栈
void STDestroy(ST* ps);void STInit(ST* ps)
{assert(ps);ps->a = NULL;ps->top = 0;ps->capacity = 0;
}void STPush(ST* ps, STDataType x)
{assert(ps);if (ps->top == ps->capacity){int newCapacity = ps->capacity == 0 ? INIT_CAPACITY : ps->capacity * 2;STDataType* tmp = (STDataType*)realloc(ps->a, sizeof(STDataType) * newCapacity);if (tmp == NULL){perror("realloc failed");exit(-1);}ps->a = tmp;ps->capacity = newCapacity;}ps->a[ps->top] = x;ps->top++;
}void STPop(ST* ps)
{assert(ps);//空assert(ps->a > 0);--ps->top;
}STDataType STTop(ST* ps)
{assert(ps);//空assert(ps->a > 0);return ps->a[ps->top - 1];
}int STSize(ST* ps)
{assert(ps);return ps->top;
}bool STEmpty(ST* ps)
{assert(ps);return ps->top == 0;
}void STDestroy(ST* ps)
{assert(ps);ps->a = NULL;ps->top = ps->capacity = 0;
}typedef struct {ST pushst;ST popst;
} MyQueue;MyQueue* myQueueCreate() {MyQueue *obj=(MyQueue*)malloc(sizeof(MyQueue));STInit(&obj->pushst);STInit(&obj->popst);return obj;
}void myQueuePush(MyQueue* obj, int x) {STPush(&obj->pushst,x);
}int myQueuePeek(MyQueue* obj) {if(STEmpty(&obj->popst)){//捯数据while(!STEmpty(&obj->pushst)){STPush(&obj->popst,STTop(&obj->pushst));STPop(&obj->pushst);}}return STTop(&obj->popst);
}int myQueuePop(MyQueue* obj) {int front=myQueuePeek(obj);STPop(&obj->popst);return front;
}bool myQueueEmpty(MyQueue* obj) {return STEmpty(&obj->popst)&&STEmpty(&obj->pushst);
}void myQueueFree(MyQueue* obj) {STDestroy(&obj->popst);STDestroy(&obj->pushst);free(obj);
}/*** Your MyQueue struct will be instantiated and called as such:* MyQueue* obj = myQueueCreate();* myQueuePush(obj, x);* int param_2 = myQueuePop(obj);* int param_3 = myQueuePeek(obj);* bool param_4 = myQueueEmpty(obj);* myQueueFree(obj);
*/