| # | Time | Username | Problem | Language | Result | Execution time | Memory |
|---|---|---|---|---|---|---|---|
| 1193113 | Unforgettablepl | COVID tests (CEOI24_covid) | C++20 | 0 ms | 0 KiB |
#include <bits/stdc++.h>
using namespace std;
/// You may use:
// The number of students
int N;
int jump;
// 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(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.
vector<bool> find_positive() {
vector<bool> answer(N);
vector<int> idxes(N);
iota(idxes.begin(),idxes.end(),0ll);
// shuffle(idxes.begin(),idxes.end(),mt19937(rand()));
auto query = [&](int a,int b){
vector<bool> q(N);
for(int i=a;i<=b;i++)q[idxes[i]]=true;
return test_students(q);
};
auto getBeforeNext = [&](int x){
if(x==N-1)return N-1;
while(true){
int tryX = min(x+jump,N-1);
if(query(x+1,tryX)){
int L = x+1;
int R = tryX;
while(L<R){
int siz = R-L+1;
long double invP = 1.0-P;
int pick = floorl((logl(1+powl(invP,siz))-logl(2))/logl(invP));
pick+=L-1;
pick = min(max(pick,L),R-1);
if(query(L,pick)){
R = pick;
} else {
L = pick+1;
}
}
return L-1;
} else {
x=tryX;
if(x==N-1)return N-1;
}
}
};
int x = getBeforeNext(-1);
while(x!=N-1){
answer[idxes[++x]]=true;
x = getBeforeNext(x);
}
return answer;
}
int main() {
int T;
scanf("%d %lf %d", &N, &P, &T);
srand(2024);
// You may perform any extra initialization here.
jump = max(1ll,floorl(-1.0/log2l(1-P)));
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;
}