Submission #1076838

#	Time	Username	Problem	Language	Result	Execution time	Memory
1076838		abouton	COVID tests (CEOI24_covid)	C++17	31.25 / 100	2032 ms	344 KiB

Main

#include <bits/stdc++.h>
using namespace std;
/// You may use:

// The number of students
int N;

// The probability any given student is positive
double P;
int K = 2;
vector<bool> answer;

// 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);
    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';
}
void tester(int a, int b)
{
    //printf("%d %d\n", a, b);
    if (b <= a) return;
    if (b==a+1)
    {
        vector<bool> quest(N);
        quest[a] = true;
        answer[a] = test_students(quest);
        return;
    }
    vector<bool> quest(N);
    for (int i = a; i < b; i ++) quest[i] = true;
    if (!test_students(quest)) return; 
    int t = (b-a)/K;
    int r = (b-a)%K;
    int nbit = 0, cur = a;
    while (cur < b)
    {
        int deb = cur;
        cur += t;
        cur += (nbit<r);
        nbit++;
        //printf("%d a %d\n", deb, cur);
        tester(deb, cur);
    }
}

/// 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.
vector<bool> find_positive() {
    answer.clear();
    answer.resize(N);
    int taille;
    if (P >= 0.3) taille = 1;
    else taille = ceil(log(0.7)/log(1-P));
    int i = 0;
    //cout << taille;
    while (i < N)
    {
        int deb = i;
        i += taille;
        i = min(i, N);
        vector<bool> quest(N);
        for (int j = deb ; j< i; j ++) quest[j] = true;
        tester(deb, i);
    }
    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;
}

Compilation message (stderr)

Main.cpp: In function 'bool test_students(std::vector<bool>)':
Main.cpp:27:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   27 |     scanf(" %c", &answer);
      |     ~~~~~^~~~~~~~~~~~~~~~
Main.cpp: In function 'int main()':
Main.cpp:86:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   86 |     scanf("%d %lf %d", &N, &P, &T);
      |     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
Main.cpp:101:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  101 |         scanf(" %c", &verdict);
      |         ~~~~~^~~~~~~~~~~~~~~~~

• Subtask 0: 0 / 0
• Subtask 1: 0 / 10
• Subtask 2: 31.249999998 / 90