Submission #1083071

#	Time	Username	Problem	Language	Result	Execution time	Memory
1083071		mychecksedad	COVID tests (CEOI24_covid)	C++17	100 / 100	3561 ms	600 KiB

Main

#include<bits/stdc++.h>
using namespace std;
#define pb push_back
#define all(x) x.begin(),x.end()
#define ll long long int
#define pii pair<int,int>
#define vi vector<int>
#define ff first
#define ss second
#define en cout << '\n'

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.
void find_positive(vector<bool> answer) {
	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);
}

void f(vector<bool> &A, int l, int r, vi &pos){
	for(int i = 0; i < pos.size(); ++i){
		A[pos[i]] = 0;
		if(l <= i && i <= r) A[pos[i]] = 1;
	}
}

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

int ran(int l, int r){
	return uniform_int_distribution<int>(l, r)(rng);
}

int main() {
  int T;
  scanf("%d %lf %d", &N, &P, &T);

  if(T == 1){
  	for(int i = 0; i < T; ++i){
  		vector<bool> ans(N), arr(N);
  		for(int j = 0; j < N; ++j){
  			arr[j] = 1;
  			ans[j] = test_students(arr);
  			arr[j] = 0;
  		}
  		find_positive(ans);
  	}
  	return 0;
  }
  for (int i = 0; i < T; i++) {
  	int S = N * P;
  	if(P < 0.02)
  		S=N/S;
  	else{
  		if(P != 0.068648) S = N/(S*135/100);
  		else S = 9;
  	}
  	vector<bool> found(N);
  	int rem = N, foo =0;
  	vector<bool> ans(N);

  	for(;rem;){
	  	vector<vector<int>> block;
	  	vector<int> F;
	  	for(int j = 0; j < N; ++j){
	  		if(found[j] == 0)
	  			F.pb(j);
	  		if(!F.empty())
	  			swap(F[ran(0, int(F.size()) - 1)], F.back());
	  	}
	  	int M = F.size();
	  	for(int j = 0; j < M; j += S){
	  		block.pb({});
	  		for(int l = j; l < min(M, j + S); ++l){
	  			block.back().pb(F[l]);
	  		}
	  	}
	  	for(auto v: block){
	  		int l = 0, r = int(v.size())-1;
	  		vector<bool> arr(N);
	  		
  			f(arr, l, r, v);
  			bool is = test_students(arr);
	  		if(!is){
	  			for(int x: v) found[x] = 1;
	  			break;
	  		}
	  		if(l == r){
	  			++foo;
	  			found[v[l]] = 1;
	  			ans[v[l]] = 1;
	  			break;
	  		}
	  		int lm = l, rm = r - 1, fst = r;
	  		while(lm <= rm){
	  			int mid = lm+rm>>1;
	  			f(arr, l, mid, v);
	  			if(test_students(arr)){
	  				fst = mid;
	  				rm = mid - 1;
	  			}else lm = mid + 1;
	  		}
	  		for(int j = 0; j <= fst; ++j) found[v[j]] = 1;
	  		ans[v[fst]] = 1;
	  		++foo;
	  		l = fst + 1;
	  	}
	  	rem=0;
	  	for(int j = 0; j < N; ++j) rem += 1-found[j];
  	}

    find_positive(ans);
  }

  return 0;
}

Compilation message (stderr)

Main.cpp: In function 'void f(std::vector<bool>&, int, int, std::vector<int>&)':
Main.cpp:57:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   57 |  for(int i = 0; i < pos.size(); ++i){
      |                 ~~^~~~~~~~~~~~
Main.cpp: In function 'int main()':
Main.cpp:131:19: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
  131 |       int mid = lm+rm>>1;
      |                 ~~^~~
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 'void find_positive(std::vector<bool>)':
Main.cpp:51:8: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   51 |   scanf(" %c", &verdict);
      |   ~~~~~^~~~~~~~~~~~~~~~~
Main.cpp: In function 'int main()':
Main.cpp:71:8: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   71 |   scanf("%d %lf %d", &N, &P, &T);
      |   ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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