Submission #1193788

#TimeUsernameProblemLanguageResultExecution timeMemory
1193788mmaitiCOVID tests (CEOI24_covid)C++20
12.48 / 100
1911 ms408 KiB
#include <bits/stdc++.h> 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'; } // test = false means we know that there is at least 1 positive result in this // range bool recurse(int L, int R, vector<bool> &ans, bool test) { vector<bool> msk(ans.size()); for (int i = L; i <= R; i++) { msk[i] = true; } bool q = true; if (test) q = test_students(msk); if (q == 1) { if (L == R) { ans[L] = true; } else { int m = (L + R) / 2; bool a1 = recurse(L, m, ans, true); if (!a1) { recurse(m + 1, R, ans, false); } else { recurse(m + 1, R, ans, true); } } } return q; } /// 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); /*int cur = (int)(1.0 / P);*/ /*cur = (1 << max(30 - __builtin_clz(cur), 1));*/ /*int init_sz = max((int)(log(0.5) / log(max(1 - P, 1e-9))), 1);*/ int init_sz = 128; int cur_sz = init_sz; int i = 0; while (i < N) { vector<bool> msk(answer.size()); for (int j = i; j <= min(i + cur_sz - 1, N - 1); j++) { msk[j] = true; } bool q = test_students(msk); if (q) { if (cur_sz == 1) { answer[i] = true; i += cur_sz; cur_sz = init_sz; } else { cur_sz /= 2; } } else { i += cur_sz; } } /*recurse(0, N - 1, answer);*/ 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:28:8: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   28 |   scanf(" %c", &answer);
      |   ~~~~~^~~~~~~~~~~~~~~~
Main.cpp: In function 'int main()':
Main.cpp:97:8: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   97 |   scanf("%d %lf %d", &N, &P, &T);
      |   ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
Main.cpp:113:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  113 |     scanf(" %c", &verdict);
      |     ~~~~~^~~~~~~~~~~~~~~~~
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