Submission #1234868

#	Time	Username	Problem	Language	Result	Execution time	Memory
1234868		laurra	COVID tests (CEOI24_covid)	C++20	51.37 / 100	790 ms	404 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(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.
vector<bool> answer;
bool divide(int st,int dr,bool keep)
{
    if(st==dr)
    {
        vector<bool> ask(N,0);
        if(keep==false)
        {
            ask[st]=1;
            answer[st]=test_students(ask);
        }
        else
        {
            answer[st]=1;
        }
        return answer[st];
    }
    if(keep==false)
    {
        vector<bool> ask(N,0);
        for(int i=st;i<=dr;i++)
        {
            ask[i]=1;
        }
        bool rasp=test_students(ask);
        if(rasp==0)
        {
            return 0;
        }
    }   
    int mijl=(st+dr)/2;
    bool pozitiv=divide(st,mijl,false);
    if(pozitiv==0)
        keep=true;
    else
        keep=false;
    divide(mijl+1,dr,keep);
    return 1;
}
vector<bool> find_positive() 
{
    int block_size=1.0*(0.65/P),i;
    answer=vector<bool>(N,0);
    i=0;
    while(i<N)
    {
        divide(i,min(i+block_size,N-1),false);
        i+=block_size+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:31:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   31 |     scanf(" %c", &answer);
      |     ~~~~~^~~~~~~~~~~~~~~~
Main.cpp: In function 'int main()':
Main.cpp:95:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   95 |     scanf("%d %lf %d", &N, &P, &T);
      |     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
Main.cpp:111:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  111 |         scanf(" %c", &verdict);
      |         ~~~~~^~~~~~~~~~~~~~~~~

• Subtask 0: 0 / 0
• Subtask 1: 0 / 10
• Subtask 2: 51.37 / 90