用两个栈（后进先出）实现队列（先进先出）

题目：232. 用栈实现队列 - 力扣（LeetCode）

typedef int STDataType;
typedef struct Stack
{STDataType* _a;//数组int _top; // 栈顶,类似顺序表中的_sizeint _capacity; // 容量
}Stack;
// 初始化栈
void StackInit(Stack* ps)
{assert(ps);ps->_a = NULL;ps->_capacity = 0;ps->_top = 0;
}
// 检测栈是否为空，如果为空返回非零结果，如果不为空返回0
bool StackEmpty(Stack* ps)
{assert(ps);return ps->_top == 0;
}
// 入栈
void StackPush(Stack* ps, STDataType data)
{assert(ps);//扩容if (ps->_capacity == ps->_top){int newcapacity = ps->_capacity == 0 ? 4 : 2 * (ps->_capacity);STDataType* tmp = (STDataType*)realloc(ps->_a, newcapacity * sizeof(STDataType));if (tmp == NULL){perror("realloc fail");return;}ps->_a = tmp;ps->_capacity = newcapacity;}ps->_a[ps->_top++] = data;
}
// 出栈
void StackPop(Stack* ps)
{assert(ps);assert(!StackEmpty(ps));ps->_top--;
}
// 获取栈顶元素
STDataType StackTop(Stack* ps)
{assert(ps);return ps->_a[ps->_top-1];
}
// 获取栈中有效元素个数
int StackSize(Stack* ps)
{assert(ps);return ps->_top;
}// 销毁栈
void StackDestroy(Stack* ps)
{assert(ps);ps->_capacity = ps->_top = 0;free(ps->_a);ps->_a = NULL;
}typedef struct {Stack Spush;Stack Spop;
} MyQueue;MyQueue* myQueueCreate() {MyQueue*p=(MyQueue*)malloc(sizeof(MyQueue));StackInit(&p->Spush);StackInit(&p->Spop);return p;
}void myQueuePush(MyQueue* obj, int x) {StackPush(&obj->Spush,x);
}
int myQueuePeek(MyQueue* obj) {if(StackEmpty(&obj->Spop)){while(!StackEmpty(&obj->Spush)){int top=StackTop(&obj->Spush);StackPush(&obj->Spop,top);StackPop(&obj->Spush);}}return StackTop(&obj->Spop);
}int myQueuePop(MyQueue* obj) {int front=myQueuePeek(obj);StackPop(&obj->Spop);return front;
}bool myQueueEmpty(MyQueue* obj) {return StackEmpty(&obj->Spop)&&StackEmpty(&obj->Spush);
}void myQueueFree(MyQueue* obj) {StackDestroy(&obj->Spop);StackDestroy(&obj->Spush);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);
*/