Submission #1134469

#	Time	Username	Problem	Language	Result	Execution time	Memory
1134469		Alihan_8	COVID tests (CEOI24_covid)	C++20	11.73 / 100	918 ms	408 KiB

Main

#include <bits/stdc++.h>

using namespace std;

#define siz(x) (int)(x).size()
#define pb push_back

/// 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';
}

const int B = 32;

/// 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.
vector<bool> find_positive() {
	int n = N;
	
	vector <bool> ans(n);
	
	for ( int i = 0; i < n; i += B ){
		int R = min(n, i + B);
		
		vector <bool> a(n);
		
		for ( int l = i; l < R; l++ ) a[l] = 1;
		
		if ( !test_students(a) ) continue;
		
		int j = i;
		
		while ( j < R ){
			int l = j - 1, r = R;
			
			while ( l + 1 < r ){
				int m = (l + r) / 2;
				
				vector <bool> a(n);
				
				for ( int x = j; x <= m; x++ ) a[x] = 1;
				
				if ( !test_students(a) ) l = m;
				else r = m;
			}
			
			if ( r == R ) break;
			
			ans[r] = true; j = r + 1;
		}
	}
	
	return ans;
}

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: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:84:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   84 |     scanf("%d %lf %d", &N, &P, &T);
      |     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
Main.cpp:100:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  100 |         scanf(" %c", &verdict);
      |         ~~~~~^~~~~~~~~~~~~~~~~

• Subtask 0: 0 / 0
• Subtask 1: 0 / 10
• Subtask 2: 11.73 / 90