【LeetCode刷题指南】--设计循环队列

typedef struct {
    int*arr;
    int front;//队头
    int rear;//队尾
    int capacity;//有效空间大小
} MyCircularQueue;


MyCircularQueue* myCircularQueueCreate(int k) {
    MyCircularQueue*cq=(MyCircularQueue*)malloc(sizeof(MyCircularQueue));
    //申请k+1个空间
    cq->arr=(int*)malloc((k+1)*sizeof(int));
    cq->front=cq->rear=0;
    cq->capacity=k;

    return cq;
}

bool myCircularQueueIsEmpty(MyCircularQueue* obj) {
    //rear==front时为空
    return obj->rear==obj->front;
}

bool myCircularQueueIsFull(MyCircularQueue* obj) {
    //(rear+1)%(k+1)==front时为满
    return (obj->rear+1)%(obj->capacity+1)==obj->front;
}

bool myCircularQueueEnQueue(MyCircularQueue* obj, int value) {
    //满了就不能插入数据
    if(myCircularQueueIsFull(obj))
    {
        return false;
    }
    //没满就插入数据，rear越界就调整回初始位置
    obj->arr[obj->rear++]=value;
    obj->rear=obj->rear%(obj->capacity+1);
    return true;
}

bool myCircularQueueDeQueue(MyCircularQueue* obj) {
    //为空不能删除
    if(myCircularQueueIsEmpty(obj))
    {
        return false;
    } 
    //不为空正常删除，front越界就调整回初始位置
    ++obj->front;
    obj->front=obj->front%(obj->capacity+1);
    return true;
}

int myCircularQueueFront(MyCircularQueue* obj) {
    //为空就不能取到队首
    if(myCircularQueueIsEmpty(obj))
    {
        return -1;
    }
    //不为空就直接返回队首元素
    return obj->arr[obj->front];
}

int myCircularQueueRear(MyCircularQueue* obj) {
     //为空就不能取到队尾
    if(myCircularQueueIsEmpty(obj))
    {
        return -1;
    }
    //不为空就直接返回队尾元素(prev,prev=rear-1),注意如果rear此时是越界后回到初始位置0的情况，特殊处理prev
    int prev=obj->rear-1;
    if(obj->rear==0)
    {
        prev=obj->capacity;
    }
    return obj->arr[prev];
}

void myCircularQueueFree(MyCircularQueue* obj) {
    if(obj->arr)
        free(obj->arr);
    free(obj);
    obj=NULL;
}

/**
 * Your MyCircularQueue struct will be instantiated and called as such:
 * MyCircularQueue* obj = myCircularQueueCreate(k);
 * bool param_1 = myCircularQueueEnQueue(obj, value);
 
 * bool param_2 = myCircularQueueDeQueue(obj);
 
 * int param_3 = myCircularQueueFront(obj);
 
 * int param_4 = myCircularQueueRear(obj);
 
 * bool param_5 = myCircularQueueIsEmpty(obj);
 
 * bool param_6 = myCircularQueueIsFull(obj);
 
 * myCircularQueueFree(obj);
*/