Submission #1231288

#	Time	Username	Problem	Language	Result	Execution time	Memory
1231288		PVM_pvm	COVID tests (CEOI24_covid)	C++20	99.12 / 100	772 ms	408 KiB

Main

#include<bits/stdc++.h>
using namespace std;
#define MAXN 1007

/// You may use:

// The number of students
int N;

// The probability any given student is positive
double P;

// This function performs a test on a subset of samples.
// Its argument is a vector of Booleans of length N,
// where the i-th element is true if the i-th sample should be added to the mix.
// It returns true if (and only if) at least one of the samples in the mix is positive.
bool test_students(vector<bool> mask) {
    assert(mask.size() == (size_t)N);

    string mask_str(N, ' ');
    for (int i = 0; i < N; i++)
        mask_str[i] = mask[i] ? '1' : '0';

    printf("Q %s\n", mask_str.c_str());
    fflush(stdout);

    char answer;
    scanf(" %c", &answer);
    return answer == 'P';
}

/// You should implement:

// This function will be called once for each test instance.
// It should use test_students to determine which samples are positive.
// It must return a vector of Booleans of length N,
// where the i-th element is true if and only if the i-th sample is positive.
bool otgov[MAXN];
void findd(int l, int r)
{
    vector<bool> nl(N,0);
    for (int q=l;q<=r;q++) nl[q]=1;
    bool otg=test_students(nl);
    if (otg)
    {
        if (l==r)
        {
            otgov[l]=1;
            return;
        }
        int mid=(l+r)/2;
        findd(l,mid);
        findd(mid+1,r);
    }
}
vector<bool> find_positive() {
    vector<bool> answer(N,0);
    int klk=1.0/P;
    klk=N;
    double curr=1-P;
    for(int i=2;i<=N;i++){
        curr*=(1-P);

        if(curr<0.460){
            klk=i-1; break;
        }
    }
    int lr=0,rr=klk-1;
    while (true)
    {
        if (lr>=N) break;
        vector<bool> nl(N,0);
        for (int q=lr;q<=rr;q++) nl[q]=1;
        bool otg;
        otg=test_students(nl);
        if (otg==0)
        {
            lr=rr+1;
            rr=lr+klk-1;
            rr=min(rr,N-1);
            continue;
        }
        int l=lr-1,r=rr;
        while (l<r-1)
        {
            int mid=(l+r)/2;
            vector<bool> nl2(N,0);
            for (int q=lr;q<=mid;q++) nl2[q]=1;
            otg=test_students(nl2);
            if (otg) r=mid;
            else l=mid;
        }
        answer[r]=1;
        lr=r+1;
        rr=lr+klk-1;
        rr=min(rr,N-1);
    }
    return answer;

}

int main() {
    int T;
    scanf("%d %lf %d", &N, &P, &T);

    // You may perform any extra initialization here.

    for (int i = 0; i < T; i++) {
        vector<bool> answer = find_positive();
        assert(answer.size() == (size_t)N);

        string answer_str(N, ' ');
        for (int j = 0; j < N; j++)
            answer_str[j] = answer[j] ? '1' : '0';

        printf("A %s\n", answer_str.c_str());
        fflush(stdout);

        char verdict;
        scanf(" %c", &verdict);
        if (verdict == 'W')
            exit(0);
    }

    return 0;
}

Compilation message (stderr)

Main.cpp: In function 'bool test_students(std::vector<bool>)':
Main.cpp:28:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   28 |     scanf(" %c", &answer);
      |     ~~~~~^~~~~~~~~~~~~~~~
Main.cpp: In function 'int main()':
Main.cpp:104:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  104 |     scanf("%d %lf %d", &N, &P, &T);
      |     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
Main.cpp:120:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  120 |         scanf(" %c", &verdict);
      |         ~~~~~^~~~~~~~~~~~~~~~~

• Subtask 0: 0 / 0
• Subtask 1: 10 / 10
• Subtask 2: 89.12 / 90