355. 設計推特

#define MAX_LEN 512

struct User {
    int userId;
    int followee[MAX_LEN]; // 散列表，0/1，1表示這個user被關注
    struct User *next;
};

struct Tweet {
    int userId;
    int tweetId;
    struct Tweet *next;
};

typedef struct {
    struct User *user;
    struct Tweet *tweet
} Twitter;


Twitter* twitterCreate() 
{
    Twitter
 
* obj = (Twitter*)malloc(sizeof(Twitter));
    obj->user = (struct User*)malloc(sizeof(struct User));
    obj->tweet = (struct Tweet*)malloc(sizeof(struct Tweet));
    obj->user->next = NULL;
    memset(obj->user->followee, 0, sizeof(int) * MAX_LEN);
    obj->tweet->next = NULL;
    
 
return obj;
}

/*
* 注意：
* 這裡只給推文這個結構體增加了userId，但是沒有給使用者這個結構體加，
* 所以後續使用者這個結構體可能會得到user是NULL，但是不能返回空
*/
void twitterPostTweet(Twitter* obj, int userId, int tweetId) 
{
    struct Tweet *node = (struct Tweet *)malloc(sizeof(struct Tweet));
    node->userId = userId;
    node->tweetId = tweetId;
    
 
// 頭插法
    node->next = obj->tweet->next;
    obj->tweet->next = node;
}

int* twitterGetNewsFeed(Twitter* obj, int userId, int* retSize) 
{
    struct User *user = obj->user->next;
    struct Tweet *tweet = obj->tweet->next;
    int *res = (int *)malloc(sizeof(int) * 10);
    *retSize = 0;
    while (user != NULL && user->userId != userId) {
        user = user->next;
    }
    if (user == NULL) {
        // 還是要遍歷推文結構體
        while (tweet != NULL && (*retSize < 10)) {
            if (tweet->userId == userId) {
                res[(*retSize)++] = tweet->tweetId;
            }
            tweet = tweet->next;
        }
        return res;
    }
    
    while (tweet != NULL && (*retSize < 10)) {
        if (tweet->userId == userId || user->followee[tweet->userId] == 1) {
            res[(*retSize)++] = tweet->tweetId;
        }
        tweet = tweet->next;
    }
    return res;
}

void twitterFollow(Twitter* obj, int followerId, int followeeId) 
{
    struct User *user = obj->user;
    // 查詢使用者連結串列中是否有這個使用者節點
    while (user->next != NULL && user->userId != followerId) {
        printf("loop \n");
        user = user->next;
    }
    // 有：設定標誌位為1
    if (user->userId == followerId) {
        user->followee[followeeId] = 1;
    } else {
        // 沒有：新建一個節點
        struct User *node = (struct User *)malloc(sizeof(struct User));
        node->userId = followerId;
        node->followee[followeeId] = 1;
        node->next = obj->user->next;
        obj->user->next = node;
    }
}

void twitterUnfollow(Twitter* obj, int followerId, int followeeId) 
{
    struct User *user = obj->user;
    while (user->next != NULL && user->userId != followerId) {
        user = user->next;
    }
    if (user->userId == followerId) {
        user->followee[followeeId] = 0;
    }
}

void twitterFree(Twitter* obj) 
{
    free(obj->user);
    free(obj->tweet);
    free(obj);
}

/**
 * Your Twitter struct will be instantiated and called as such:
 * Twitter* obj = twitterCreate();
 * twitterPostTweet(obj, userId, tweetId);
 
 * int* param_2 = twitterGetNewsFeed(obj, userId, retSize);
 
 * twitterFollow(obj, followerId, followeeId);
 
 * twitterUnfollow(obj, followerId, followeeId);
 
 * twitterFree(obj);
*/