the questions about scanf() and cin-CodePudding

I met a questions. the link -> the problem here is my solution.If i use scanf, the code can be accepted on codeforces, but replace cin then not,it occurs wrong answer,but in my local interpreter using cin is ok. why?

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int t;
    scanf("%d", &t);
    nt :
    while (t--) {
        long long hc, dc, hm, dm, w, a;
        long k;
        scanf("%lld%lld%lld%lld%d%lld%lld", &hc, &dc, &hm, &dm, &k, &w, &a); // ok
//        cin >> hc >> dc >> hm >> dm >> k >> w >> a; // cannot work
        for (int i = 0; i < k   1; i  ) {
            int opt = k - i;
            long long hc1 = opt * a   hc;
            long long dc1 = i * w   dc;
            long long cnt1 = hm / dc1   (hm % dc1 > 0);
            long long cnt2 = hc1 / dm   (hc1 % dm > 0);
            if (cnt1 <= cnt2) {
                printf("YES\n");
                goto nt;
            }
        }
        printf("NO\n");
    }
}

I just try a lot of practices , found the key of question is input of question.

CodePudding user response：

You have another scanf in line 5 which you have to replace too. Otherwise they each have their own buffers of the input and get mixed up.