Submission #1114842

#	Time	Username	Problem	Language	Result	Execution time	Memory
1114842		PagodePaiva	COVID tests (CEOI24_covid)	C++17	0 / 100	5565 ms	91548 KiB

Main

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

set <int> find(vector <bool> at){
  int con = 0;
  for(auto x : at){
    if(x) con++;
  }
  if(con == 1){
    set <int> ans;
    for(int i = 0;i < at.size();i++){
      if(at[i]){
        ans.insert(i);
      }
    }
    return ans;
  }
  int d;
  vector <bool> nw;
  vector <bool> nw2;
  for(int i = 0;i < N;i++){
    nw.push_back(false);
    nw2.push_back(false);
  }
  for(int i = 0;i < at.size();i++){
    if(at[i]){
      if(d < con/2) nw[i] = true;
      else nw2[i] = true;
      d++;
    }
  }
  set <int> ans;
  if(test_students(nw)){
    set <int> aux = find(nw);
    for(auto x : aux)
      ans.insert(x);
  }
  if(test_students(nw2)){
    set <int> aux = find(nw2);
    for(auto x : aux){
      ans.insert(x);
    }
  }
  return ans;
}

std::vector<bool> find_positive() {
    vector <int> v;
    int n = N;
    for(int i = 0;i < n;i++){
      v.push_back(i);
    }
    random_shuffle(v.begin(), v.end());
    double p = P;
    int tam = 1;
    while(p > 0.5){
      p *= P;
      tam++;
    }
    tam--;
    if(tam == 0) tam++;
    vector <bool> res;
    for(int i = 0;i < n;i++){
      res.push_back(false);
    }
    for(int i = 0;i < n;i += tam){
      vector <bool> s;
      for(int j = 0;j < n;j++){
        s.push_back(false);
      }
      for(int j = i;j < i+tam;j++){
        s[v[j]] = true;
      }
      bool ans = test_students(s);
      if(!ans) continue;
      set <int> aa = find(s);
      for(auto x : aa){
        //cout << x << ' ';
        res[x] = true; 
      }
    }
    return res;
}

int main() {
    srand(time(0));
    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 'std::set<int> find(std::vector<bool>)':
Main.cpp:50:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<bool>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   50 |     for(int i = 0;i < at.size();i++){
      |                   ~~^~~~~~~~~~~
Main.cpp:64:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<bool>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   64 |   for(int i = 0;i < at.size();i++){
      |                 ~~^~~~~~~~~~~
Main.cpp: In function 'bool test_students(std::vector<bool>)':
Main.cpp:32:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   32 |     scanf(" %c", &answer);
      |     ~~~~~^~~~~~~~~~~~~~~~
Main.cpp: In function 'int main()':
Main.cpp:127:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  127 |     scanf("%d %lf %d", &N, &P, &T);
      |     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
Main.cpp:143:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  143 |         scanf(" %c", &verdict);
      |         ~~~~~^~~~~~~~~~~~~~~~~
Main.cpp: In function 'std::set<int> find(std::vector<bool>)':
Main.cpp:68:8: warning: 'd' may be used uninitialized in this function [-Wmaybe-uninitialized]
   68 |       d++;
      |       ~^~

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