Friend Suggestion

#define MAXL            5
#define MAXF            10
#define MAXU            10001
#define MAXC            315
#define NBIT            sizeof(unsigned int) * 8

unsigned int fStatus[MAXU][MAXC];
int N = 0, C = 0, d = 0;

void init(int n){
    d = NBIT;
    N = n, C = (n / d) + 1;
    for (int i = 0; i <= N; i++){
        for (int j = 0; j <= C; j++)
            fStatus[i][j] = 0;
    }
}

void add(int id, int F, int ids[MAXF]){
    int r1 = id / d, c1 = id % d;
    for (int i = 0; i < F; i++){
        int r2 = ids[i] / d, c2 = ids[i] % d;
        fStatus[id][r2] = (fStatus[id][r2] | (1 << c2));
        fStatus[ids[i]][r1] = (fStatus[ids[i]][r1] | (1 << c1));
    }
}

void del(int id1, int id2){
    int r1 = id1 / d, c1 = id1 % d;
    int r2 = id2 / d, c2 = id2 % d;
    fStatus[id1][r2] = (fStatus[id1][r2] ^ (1 << c2));
    fStatus[id2][r1] = (fStatus[id2][r1] ^ (1 << c1));
}

int  recommend(int id, int list[MAXL]){
    int tmp[MAXL+ 1], fnd[MAXU], n = 0;
    for (int i = 1; i <= N; i++)
        fnd[i] = 0;
    for (int i = 0; i <= C; i++){
        if (fStatus[id][i]){
            for (int j = 0; j < 32; j++){
                if ((fStatus[id][i] & (1 << j))){
                    int f = 32 * i + j;
                    for (int k = 0; k <= C; k++){
                        if (fStatus[f][k]){
                            for (int l = 0; l < 32; l++){
                                if (fStatus[f][k] & (1 << l)){
                                    int ff = 32 * k + l;
                                    fnd[ff]++;
                                }
                            }
                        }
                    }
                }
            }
        }
    }

    int r1 = id / d, c1 = id % d;
    for (int i = 1; i <= N; i++){
        int r2 = i / d, c2 = i % d;
        if (i == id || !fnd[i] || (fStatus[id][r2] & (1 << c2)))
            continue;

        tmp[n] = i;
        for (int j = n; j > 0; j--){
            if (fnd[i] > fnd[tmp[j - 1]]){
                int tp = tmp[j - 1];
                tmp[j - 1] = i;
                tmp[j] = tp;
            }
        }
        n = (n >= 5) ? n : n + 1;
    }

    for (int i = 0; i < 5 && i < n; i++)
        list[i] = tmp[i];

    return n;
}