请你仅使用两个栈实现先入先出队列。队列应当支持一般队列支持的所有操作(push、pop、peek、empty):
实现 MyQueue 类:
void push(int x) 将元素 x 推到队列的末尾
int pop() 从队列的开头移除并返回元素
int peek() 返回队列开头的元素
boolean empty() 如果队列为空,返回 true ;否则,返回 false
来源:力扣(LeetCode)
链接:https://leetcode-cn.com/problems/implement-queue-using-stacks
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代码是力扣官方给出的代码
//首先是创建栈的过程
typedef struct {
int* stk;
int stkSize;
int stkCapacity;
} Stack;
Stack* stackCreate(int cpacity) {
Stack* ret = malloc(sizeof(Stack));
ret->stk = malloc(sizeof(int) * cpacity);
ret->stkSize = 0;
ret->stkCapacity = cpacity;
return ret;
}
void stackPush(Stack* obj, int x) {
obj->stk[obj->stkSize++] = x;
}
void stackPop(Stack* obj) {
obj->stkSize--;
}
int stackTop(Stack* obj) {
return obj->stk[obj->stkSize - 1];
}
bool stackEmpty(Stack* obj) {
return obj->stkSize == 0;
}
void stackFree(Stack* obj) {
free(obj->stk);
}
//开始创建队列
typedef struct {
Stack* inStack;
Stack* outStack;
} MyQueue;
MyQueue* myQueueCreate() {
MyQueue* ret = malloc(sizeof(MyQueue));
ret->inStack = stackCreate(100);
ret->outStack = stackCreate(100);
return ret;
}
void in2out(MyQueue* obj) {
while (!stackEmpty(obj->inStack)) {
stackPush(obj->outStack, stackTop(obj->inStack));
stackPop(obj->inStack);
}
}
void myQueuePush(MyQueue* obj, int x) {
stackPush(obj->inStack, x);
}
int myQueuePop(MyQueue* obj) {
if (stackEmpty(obj->outStack)) {
in2out(obj);
}
int x = stackTop(obj->outStack);
stackPop(obj->outStack);
return x;
}
int myQueuePeek(MyQueue* obj) {
if (stackEmpty(obj->outStack)) {
in2out(obj);
}
return stackTop(obj->outStack);
}
bool myQueueEmpty(MyQueue* obj) {
return stackEmpty(obj->inStack) && stackEmpty(obj->outStack);
}
void myQueueFree(MyQueue* obj) {
stackFree(obj->inStack);
stackFree(obj->outStack);
}