【算法集训】基础数据结构：五、队列(续)

第二题 LCR 041. 数据流中的移动平均值

https://leetcode.cn/problems/qIsx9U/description/

typedef struct {
    int head;  //记录头部
    int tail;  //记录尾部
    int size;  //记录长度
    int data[10001];  //记录每个数据
    double sum;  //记录队列的和

} MovingAverage;

/** Initialize your data structure here. */

MovingAverage* movingAverageCreate(int size) {
    MovingAverage * obj = (MovingAverage *)malloc(sizeof(MovingAverage));
    obj->head = 0;
    obj->tail = -1;
    obj->size = size;
    obj->sum = 0;
    return obj;
}

double movingAverageNext(MovingAverage* obj, int val) {
    obj->data[++obj->tail] = val;
    obj->sum += val;
    if(obj->tail - obj->head + 1 > obj->size) {
        obj->sum -= obj->data[obj->head];
        ++obj->head;
    }
    int size = obj->tail - obj->head + 1; //当前队列的长度
    return obj->sum / size;
}

void movingAverageFree(MovingAverage* obj) {

}

/**
 * Your MovingAverage struct will be instantiated and called as such:
 * MovingAverage* obj = movingAverageCreate(size);
 * double param_1 = movingAverageNext(obj, val);
 
 * movingAverageFree(obj);
*/

第三题 1700. 无法吃午餐的学生数量

https://leetcode.cn/problems/number-of-students-unable-to-eat-lunch/description/

int countStudents(int* students, int studentsSize, int* sandwiches, int sandwichesSize) {
    int head = 0;
    int tail = -1;
    int data[100001];
    for(int i = 0; i < studentsSize; ++i) {
        data[++tail] = students[i];
    }
    int sandIdx = 0;
    int gg = 0;  //如果一直不满足条件防止无限循环下去
    while(head <= tail) {
        if(data[head] == sandwiches[sandIdx]) {
            // 如果相等的话当前学生会拿走食物,所以head++退出队列
            ++head;
            ++sandIdx;
            // 如果遍历完都满足,则返回0; 
            if(sandwichesSize == sandIdx) {  //这里sandwichesSize不-1的原因是上面sandIdx满足条件后+1,所以这里直接比
                return 0;
            }
        }else {
            data[++tail] = data[head];
            head++;
            if(gg++ > 10000) {
                return tail - head + 1;
            }
        }
    }
    return tail - head + 1;
}