Submission #1177619

#	Time	Username	Problem	Language	Result	Execution time	Memory
1177619		alexdd	COVID tests (CEOI24_covid)	C++20	14.29 / 100	1829 ms	396 KiB

Main

#include <cassert>
#include <cstdio>
#include <string>
#include <vector>
using namespace std;
typedef long double ld;
const int INF = 1e9;
/// You may use:

// The number of students
int N;

// The probability any given student is positive
ld 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.
int get_mij(int st, int dr)
{
    if(P > 0.03)
        return st;
    return (st+dr)/2;


    vector<ld> primu(N);
    for(int i=st;i<=dr;i++)
    {
        ld cur=1;
        for(int j=st;j<i;j++)
            cur = cur * ((ld)1-P);
        cur = cur * P;

        primu[i] = cur;
    }


    ld best=INF;
    int unde=st;
    for(int i=st;i<=dr;i++)
    {
        ld ple=0,pri=0;
        for(int u=st;u<i;u++)
            ple += primu[u];
        for(int u=i+1;u<=dr;u++)
            pri += primu[u];
        if(abs(ple-pri) < best)
        {
            best = abs(ple-pri);
            unde = i;
        }
    }

    return unde;
}
std::vector<bool> find_positive()
{
    std::vector<bool> answer(N);

    int poz=0;
    while(poz<N)
    {
        int st=poz,dr=N-1,ans=-1;
        while(st<=dr)
        {
            int mij = get_mij(st,dr);
            vector<bool> ask(N,0);
            for(int i=poz;i<=mij;i++)
                ask[i]=1;
            if(test_students(ask))
            {
                ans = mij;
                dr = mij-1;
            }
            else
            {
                st = mij+1;
            }
        }
        if(ans==-1)
            break;
        answer[ans] = 1;
        poz = ans+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++) {
        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 'int main()':
Main.cpp:113:17: warning: format '%lf' expects argument of type 'double*', but argument 3 has type 'ld*' {aka 'long double*'} [-Wformat=]
  113 |     scanf("%d %lf %d", &N, &P, &T);
      |               ~~^          ~~
      |                 |          |
      |                 double*    ld* {aka long double*}
      |               %Lf
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:113:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  113 |     scanf("%d %lf %d", &N, &P, &T);
      |     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
Main.cpp:129:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  129 |         scanf(" %c", &verdict);
      |         ~~~~~^~~~~~~~~~~~~~~~~

• Subtask 0: 0 / 0
• Subtask 1: 0 / 10
• Subtask 2: 14.29 / 90