232. Implement Queue using Stacks

Implement the following operations of a queue using stacks.

• push(x) -- Push element x to the back of queue.
• pop() -- Removes the element from in front of queue.
• peek() -- Get the front element.
• empty() -- Return whether the queue is empty.

这里定义了一个指向数组的指针和数组容量的最大值MaxSize，如果数组中的数据的个数小于MaxSize，那么利用指针给数组加上一个数据，如果数组的大小等于MaxSize，那么所有数据前移一位，在数组最后一位放入新到达的数据。

typedef struct {    int num;    int* arr;    int MaxSize;} MyQueue;/** Initialize your data structure here. */MyQueue* myQueueCreate(int maxSize) {    MyQueue* queue;    queue=malloc(sizeof(MyQueue));    queue->num=0;    queue->arr=(int*)malloc(sizeof(int)*maxSize);    queue->MaxSize=maxSize;    return queue;}/** Push element x to the back of queue. */void myQueuePush(MyQueue* obj, int x) {    if(obj->num==obj->MaxSize){        for(int i=0;i<obj->num-1;i++)           obj->arr[i]=obj->arr[i+1];      obj->arr[obj->num-1]=x;         }    else{        obj->arr[obj->num]=x;        obj->num++;    }    }/** Removes the element from in front of queue and returns that element. */int myQueuePop(MyQueue* obj) {    int p;    p=obj->arr[0];    for(int i=0;i<obj->num-1;i++)    obj->arr[i]=obj->arr[i+1];    obj->num--;    return p;}/** Get the front element. */int myQueuePeek(MyQueue* obj) {    return(obj->arr[0]);}/** Returns whether the queue is empty. */bool myQueueEmpty(MyQueue* obj) {    return obj->num==0;}void myQueueFree(MyQueue* obj) {    obj->num=0;}/** * Your MyQueue struct will be instantiated and called as such: * struct MyQueue* obj = myQueueCreate(maxSize); * myQueuePush(obj, x); * int param_2 = myQueuePop(obj); * int param_3 = myQueuePeek(obj); * bool param_4 = myQueueEmpty(obj); * myQueue Free(obj); */