Submission #1218242

#TimeUsernameProblemLanguageResultExecution timeMemory
1218242j_vdd16COVID tests (CEOI24_covid)C++20
34.65 / 100
7058 ms416 KiB
#include <cassert> #include <cstdio> #include <string> #include <vector> /// 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'; } using namespace std; void solve(std::vector<bool>& result, const std::vector<int>& students, double p) { double probAllNegative = 1.0; int count = 0; while (probAllNegative > 0.5) { probAllNegative *= 1.0 - p; count++; } if (0.5 - probAllNegative > probAllNegative / (1.0 - p) - 0.5) count--; int n = students.size(); std::vector<int> newStudents; for (int i = 0; i < n; i += count) { std::vector<bool> mask(N); for (int j = i; j < min(n, i + count); j++) { mask[students[j]] = true; } bool res = test_students(mask); if (res && count == 1) { result[students[i]] = true; } else if (res) { for (int j = i; j < min(n, i + count); j++) { newStudents.push_back(students[j]); } } } if (newStudents.size()) { double pPos = 1.0 / double(count); double newP = pPos * 1.0 + (1 - pPos) * p; solve(result, newStudents, newP); } } /// 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> find_positive() { std::vector<bool> answer(N); std::vector<int> students(N); for (int i = 0; i < N; i++) students[i] = i; solve(answer, students, P); 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 'bool test_students(std::vector<bool>)':
Main.cpp:29:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   29 |     scanf(" %c", &answer);
      |     ~~~~~^~~~~~~~~~~~~~~~
Main.cpp: In function 'int main()':
Main.cpp:91:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   91 |     scanf("%d %lf %d", &N, &P, &T);
      |     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
Main.cpp:107:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  107 |         scanf(" %c", &verdict);
      |         ~~~~~^~~~~~~~~~~~~~~~~
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