Submission #1234911

#	Time	Username	Problem	Language	Result	Execution time	Memory
1234911		trimkus	COVID tests (CEOI24_covid)	C++20	0 / 100	1 ms	408 KiB

Main

#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';
}

/// 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.

bool query(int l, int r) {
	vector<bool> qr(N);
	for (int i = l; i <= r; ++i) {
		qr[i] = 1;
	}
	return test_students(qr);
}

std::vector<bool> find_positive() {
    std::vector<bool> answer(N);
	auto dfs = [&](auto& dfs, int l, int r) -> void {
		if (l == r) {
			answer[l] = 1;
			return;
		}
		int m = (l + r) / 2;
		if (query(l, m)) {
			dfs(dfs, l, m);
			if (r - l > 100 * P) {
				if (query(m + 1, r)) dfs(dfs, m + 1, r);
			}
		} else {
			dfs(dfs, m + 1, r);
		}
		
	};
	dfs(dfs, 0, N - 1);
    return answer;
}


void solve() {
	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);
}

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++) {
        solve();
    }

    return 0;
}

Compilation message (stderr)

Main.cpp: In function 'bool test_students(std::vector<bool>)':
Main.cpp:27:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   27 |     scanf(" %c", &answer);
      |     ~~~~~^~~~~~~~~~~~~~~~
Main.cpp: In function 'void solve()':
Main.cpp:81:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   81 |         scanf(" %c", &verdict);
      |         ~~~~~^~~~~~~~~~~~~~~~~
Main.cpp: In function 'int main()':
Main.cpp:88:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   88 |     scanf("%d %lf %d", &N, &P, &T);
      |     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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