Submission #1044555

#	Time	Username	Problem	Language	Result	Execution time	Memory
1044555		SamAnd	COVID tests (CEOI24_covid)	C++17	10 / 100	941 ms	596 KiB

Main

#include <cassert>
#include <cstdio>
#include <string>
#include <vector>
using namespace std;

/// 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(std::vector<bool> mask) {
    assert(mask.size() == (size_t)N);

    std::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:

bool rec(int l, int r, vector<bool>& answer, bool z)
{
    if (!z)
    {
        double t = 1;
        for (int i = 0; i < r - l + 1; ++i)
            t *= (1 - P);
        if (l == r || t > 0.001)
        {
            vector<bool> v(N, false);
            for (int i = l; i <= r; ++i)
                v[i] = true;
            if (test_students(v) == false)
                return false;
        }
        if (l == r)
        {
            answer[l] = true;
            return true;
        }
        int m = (l + r) / 2;
        bool zz = rec(l, m, answer, false);
        rec(m + 1, r, answer, (zz ^ true));
        return true;
    }
    else
    {
        if (l == r)
        {
            answer[l] = true;
            return true;
        }
        int m = (l + r) / 2;
        bool zz = rec(l, m, answer, false);
        rec(m + 1, r, answer, (zz ^ true));
        return true;
    }
}

// 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.
std::vector<bool> find_positive() {
    std::vector<bool> answer(N, false);
    rec(0, N - 1, answer, false);
    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++) {
        std::vector<bool> answer = find_positive();
        assert(answer.size() == (size_t)N);

        std::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;
}

// 1000 0.001 300
// 1000 0.005256 300
// 1000 0.011546 300
// 1000 0.028545 300
// 1000 0.039856 300
// 1000 0.068648 300
// 1000 0.104571 300
// 1000 0.158765 300
// 1000 0.2 300

Compilation message (stderr)

Main.cpp: In function 'bool test_students(std::vector<bool>)':
Main.cpp:30:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   30 |     scanf(" %c", &answer);
      |     ~~~~~^~~~~~~~~~~~~~~~
Main.cpp: In function 'int main()':
Main.cpp:87:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   87 |     scanf("%d %lf %d", &N, &P, &T);
      |     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
Main.cpp:103:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  103 |         scanf(" %c", &verdict);
      |         ~~~~~^~~~~~~~~~~~~~~~~

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