题海拾贝：力扣 232.用栈实现队列

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1、题目

题目链接：232. 用栈实现队列 - 力扣（LeetCode） 

2、题解 

//快速写一下
typedef int STdate;
typedef struct stack
{
	STdate* arr;//数组模拟栈
	int top;
	int capacity;
}ST;
void InitST(ST* stack)
{
	stack->arr = NULL;
	stack->capacity = 0;//能存放的最大数据个数
	stack->top = 0;//有效数据个数
}
void Destory(ST* stack)
{
	if (stack->arr)
	{
		free(stack->arr);
		stack->arr = NULL;
	}
	stack->capacity = 0;//能存放的最大数据个数
	stack->top = 0;//有效数据个数
}
void STpush(ST* stack, STdate x)
{
	assert(stack);
	//判断是否还有空间
	if (stack->top == stack->capacity)
	{
		int newcapacity = stack->capacity ? 2 * stack->capacity : 1;
		STdate* p = (STdate*)realloc(stack->arr, newcapacity * sizeof(int));
		if (p == NULL)
		{
			exit(1);
		}
		stack->arr = p;
		stack->capacity = newcapacity;
	}
	stack->arr[stack->top] = x;
	stack->top++;
}
bool STempty(ST* stack)
{
	if (stack->top != 0)
	{
		return false;
	}
	else
	{
		return true;
	}
}
void STpop(ST* stack)
{
	assert(!STempty(stack));
	stack->top--;
}
int STsize(ST* stack)
{
	return stack->top;
}
int STtop(ST* stack)
{
	assert(stack);
	return stack->arr[stack->top - 1];
}
//以上是栈的操作

typedef struct {
    //包含两个栈
    ST STpush;
    ST STpop;
} MyQueue;

//初始化
MyQueue* myQueueCreate() {
    MyQueue* qu=(MyQueue*)malloc(sizeof(MyQueue));
    InitST(&qu->STpush);
    InitST(&qu->STpop);
    return qu;
}

void myQueuePush(MyQueue* obj, int x) {
    //插入元素就往插入元素的栈里插入就行
    STpush(&obj->STpush,x);
}

int myQueuePop(MyQueue* obj) {
    //在删除栈为空的情况下
    //删除需要把插入栈里的所有元素都转移到删除栈里，然后再弹出栈顶
    if(STempty(&obj->STpop))
    {
        while(!STempty(&obj->STpush))
        {
        STpush(&obj->STpop,STtop(&obj->STpush));
        STpop(&obj->STpush);
        }
    }
    int ele=STtop(&obj->STpop);
    STpop(&obj->STpop);
    return ele;
}

int myQueuePeek(MyQueue* obj) {
    //在删除栈为空的情况下
    //删除需要把插入栈里的所有元素都转移到删除栈里，然后再弹出栈顶
    if(STempty(&obj->STpop))
    {
        while(!STempty(&obj->STpush))
        {
        STpush(&obj->STpop,STtop(&obj->STpush));
        STpop(&obj->STpush);
        }
    }
    int ele=STtop(&obj->STpop);//队列开头元素
    return ele;
}

bool myQueueEmpty(MyQueue* obj) {
    return STempty(&obj->STpush)&&STempty(&obj->STpop);
}

void myQueueFree(MyQueue* obj) {
    Destory(&obj->STpush);
    Destory(&obj->STpop);
    free(obj);
    obj=NULL;
}

/**
 * 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);
*/

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