Submission #1116560

#	Time	Username	Problem	Language	Result	Execution time	Memory
1116560		ortsac	COVID tests (CEOI24_covid)	C++17	79.71 / 100	7060 ms	508 KiB

Main

//#pragma GCC optimize("O3")
#include <bits/stdc++.h>

using namespace std;

/// You may use:

// The number of students
int N;
int eQtd, eAparece;

// 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(const 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:

// 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_positive1() {
    int n = N;
    vector<bool> answer(n);
    int qtd = 0;
    int curr = -1;
    while (curr < (n - 1)) {
        //if (qtd >= eQtd) {
        //    vector<bool> mask(n);
        //    for (int i = curr + 1; i < n; i++) mask[i] = 1;
        //    if (!test_students(mask)) break;
        //}
        int l = curr + 1, r = n - 1, ans = n;
        while (l <= r) {
            int m1 = (l + eAparece);
            int m2 = (l + r)/2;
            int m = min(m1, m2);
            vector<bool> mask(n);
            for (int i = curr + 1; i <= m; i++) mask[i] = 1;
            if (test_students(mask)) {
                ans = m;
                r = m - 1;
            } else {
                l = m + 1;
            }
        }
        curr = ans;
        if (curr != n) answer[curr] = 1;
        qtd++;
    }
    return answer;
}

vector<bool> find_positive2() {
    int n = N;
    vector<bool> answer(n);
    int qtd = 0;
    int curr = -1;
    while (curr < (n - 1)) {
        if (qtd >= eQtd) {
            vector<bool> mask(n);
            for (int i = curr + 1; i < n; i++) mask[i] = 1;
            if (!test_students(mask)) break;
        }
        int l = curr + 1, r = n - 1, ans = n;
        while (l <= r) {
            int m1 = (l + eAparece);
            int m2 = (l + r)/2;
            int m = min(m1, m2);
            vector<bool> mask(n);
            for (int i = curr + 1; i <= m; i++) mask[i] = 1;
            if (test_students(mask)) {
                ans = m;
                r = m - 1;
            } else {
                l = m + 1;
            }
        }
        curr = ans;
        if (curr != n) answer[curr] = 1;
        qtd++;
    }
    return answer;
}

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

    // You may perform any extra initialization here.
    eQtd = (((double) N) * P);
    eAparece = 0;
    double pos = 1.0;
    while (pos > 0.5) {
        pos *= (1.0 - P);
        eAparece++;
    }
    for (int i = 0; i < T; i++) {
        std::vector<bool> answer;
        if (P > 0.02) answer = find_positive1();
        else answer = find_positive2();
        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(const 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:106:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  106 |     scanf("%d %lf %d", &N, &P, &T);
      |     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
Main.cpp:130:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  130 |         scanf(" %c", &verdict);
      |         ~~~~~^~~~~~~~~~~~~~~~~

• Subtask 0: 0 / 0
• Subtask 1: 0 / 10
• Subtask 2: 79.710000003 / 90