Submission #1090376

#	Time	Username	Problem	Language	Result	Execution time	Memory
1090376		lucri	COVID tests (CEOI24_covid)	C++17	54.19 / 100	1894 ms	344 KiB

Main

#include <bits/stdc++.h>
/// 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:

// 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> answer;
std::vector<bool> test;
std::vector<int> ind;
bool raspunde(int b,int e,bool ok)
{
    for(int i=b;i<=e;++i)
        test[ind[i]]=1;
    bool ver=ok;
    if(ok==0)
        ver=test_students(test);
    for(int i=b;i<=e;++i)
        test[ind[i]]=0;
    if(b==e)
    {
        if(ver)
            answer[ind[b]]=true;
        return ver;
    }
    if(ver)
    {
        if(e-b+1>=4)
        {
            int b1=b+(e-b)/3;
            int b2=b+2*(e-b)/3;
            ok=raspunde(b,b1,0)|raspunde(b1+1,b2,0);
            raspunde(b2+1,e,!ok);
        }
        else
        {
            int k=rand()%2;
            if(k==1)
            {
                ok=raspunde(b,(b+e)/2,0);
                raspunde((b+e)/2+1,e,!ok);
            }
            else
            {
                ok=raspunde((b+e)/2+1,e,0);
                raspunde(b,(b+e)/2,!ok);
            }
        }
    }
    return ver;
}
std::vector<bool> find_positive()
{
    for(int i=0;i<N;++i)
    {
        answer[i]=test[i]=0;
        ind[i]=i;
    }
    random_shuffle(ind.begin(),ind.end());
    if(P>0.2)//subtask 1
    {
        for(int i=0;i<N;++i)
        {
            test[i]=true;
            answer[i]=test_students(test);
            test[i]=false;
        }
    }
    else if(P>0.17)//P=0.2
    {
        for(int i=0;i<N;i+=4)
            raspunde(i,std::min(N-1,i+3),0);
    }
    else if(P>0.11)//P=0.158765
    {
        for(int i=0;i<N;i+=8)
            raspunde(i,std::min(N-1,i+7),0);
    }
    else if(P>0.1)//P=0.104571
    {
        for(int i=0;i<N;i+=16)
            raspunde(i,std::min(N-1,i+15),0);
    }
    else if(P>0.06)//P=0.068648
    {
        for(int i=0;i<N;i+=8)
            raspunde(i,std::min(N-1,i+7),0);
    }
    else if(P>0.03)//P=0.039856
    {
        for(int i=0;i<N;i+=60)
            raspunde(i,std::min(N-1,i+59),0);
    }
    else if(P>0.02)//P=0.028545
    {
        for(int i=0;i<N;i+=25)
            raspunde(i,std::min(N-1,i+24),0);
    }
    else if(P>0.01)//P=0.011546
    {
        for(int i=0;i<N;i+=120)
            raspunde(i,std::min(N-1,i+119),0);
    }
    else if(P>0.005)//P=0.005256
    {
        for(int i=0;i<N;i+=105)
            raspunde(i,std::min(N-1,i+104),0);
    }
    else
    {
        raspunde(0,(N-1)/2,0);
        raspunde((N-1)/2+1,N-1,0);
    }
    return answer;
}

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

    // You may perform any extra initialization here.
    srand(time(0));
    answer.resize(N);
    ind.resize(N);
    test.resize(N);
    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:25:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   25 |     scanf(" %c", &answer);
      |     ~~~~~^~~~~~~~~~~~~~~~
Main.cpp: In function 'int main()':
Main.cpp:146:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  146 |     scanf("%d %lf %d", &N, &P, &T);
      |     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
Main.cpp:165:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  165 |         scanf(" %c", &verdict);
      |         ~~~~~^~~~~~~~~~~~~~~~~

• Subtask 0: 0 / 0
• Subtask 1: 10 / 10
• Subtask 2: 44.19 / 90