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Submission #1076858

# Submission time Handle Problem Language Result Execution time Memory
1076858 2024-08-26T17:26:17 Z anton COVID tests (CEOI24_covid) C++17
46.34 / 100
 7000 ms 428 KB 
#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;

int group_sz =1;
// 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 test_single(int u){
    vector<bool> mask(N, false);
    mask[u] = true;
    return test_students(mask);
}

bool test_inter(int l, int r){
    vector<bool> mask(N, false);
    for(int i = l; i<=r; i++){
        mask[i] = true;
    }
    return test_students(mask);
}

int split_len[1001];

void do_split(int l, int r,vector<bool>& ans){
    if(l==r){
        ans[l] = true;
        return;
    }
    int opti_len = split_len[r-l+1];
    if(test_inter(l, l+opti_len-1)){
        do_split(l, l+opti_len-1, ans);
        if(test_inter(l+opti_len, r)){
            do_split(l+opti_len, r, ans);
        }
    }
    else{
        do_split(l+opti_len, r, ans);
    }
}
std::vector<bool> find_positive() {
    std::vector<bool> answer(N);

   if(test_inter(0, N-1)){
    do_split(0, N-1, answer);
   }
    
    /*for(int i = 0; i<N; i+=group_sz){
        vector<bool>cur_mask (N, false);

        vector<int> order;
        for(int j = i; j<min(i+group_sz, N); j++){
            cur_mask[j] = true;
        }    
        
        if(test_students(cur_mask)){
            bool found = false;
            for(int j = i; j<min(i+group_sz, N); j++){
                answer[j] = test_single(j);
                cur_mask[j] = false;
                if(answer[j] && j<min(i+group_sz, N)-1){
                    if(!test_students(cur_mask)){
                        break;
                    }
                }
            }
        }
    }*/


    return answer;
}

int get_sz(double p, double target){
    int res = 1;
    double cur_p = p;
    while(cur_p>0.5){
        res ++;
        cur_p*=p;
    }
    return res;
}

double at_least_1(int len){
    return 1.-pow(1.-P, len);
}
int main() {
    int T;
    scanf("%d %lf %d", &N, &P, &T);

    // You may perform any extra initialization here.
    group_sz= min(max(get_sz((1.-P), 0.5), 1), N/2);

    vector<double> expected_turns(N+1, 1e18);
    for(int i = 1; i<=N; i++){
        if(i==1){
            expected_turns[i] = 0.;
        }
        else{
            for(int j = 1; j<i; j++){
                double total = at_least_1(j) * pow(1.-P, i-j) + at_least_1(i-j) * pow(1.-P, j) +at_least_1(j)*at_least_1(i-j);
                double prop_j = (at_least_1(j) * pow(1.-P, i-j) + at_least_1(j)*at_least_1(i-j))/total;
                double prop_both = (at_least_1(j)*at_least_1(i-j))/total;
                double prop_i = (at_least_1(i-j) * pow(1.-P, j) + at_least_1(j)*at_least_1(i-j))/total;
                double other = 1.+prop_j + prop_j*expected_turns[j] +prop_i* expected_turns[i-j];
                if(other< expected_turns[i]){
                    split_len[i] = j;
                    expected_turns[i]= other;
                }
            
            }
        }
    }
    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

Main.cpp: In function 'int main()':
Main.cpp:132:24: warning: unused variable 'prop_both' [-Wunused-variable]
  132 |                 double prop_both = (at_least_1(j)*at_least_1(i-j))/total;
      |                        ^~~~~~~~~
Main.cpp: In function 'bool test_students(std::vector<bool>)':
Main.cpp:28:10: 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:118:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  118 |     scanf("%d %lf %d", &N, &P, &T);
      |     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
Main.cpp:155:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  155 |         scanf(" %c", &verdict);
      |         ~~~~~^~~~~~~~~~~~~~~~~

Subtask #0
0.0 / 0.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 344 KB Output is correct

Subtask #1
0.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 227 ms 416 KB Output is correct
2 Correct 179 ms 416 KB Output is correct
3 Correct 205 ms 412 KB Output is correct
4 Correct 177 ms 428 KB Output is correct
5 Correct 210 ms 416 KB Output is correct
6 Correct 214 ms 344 KB Output is correct
7 Correct 156 ms 344 KB Output is correct
8 Correct 153 ms 416 KB Output is correct
9 Correct 142 ms 344 KB Output is correct
10 Correct 131 ms 412 KB Output is correct
11 Correct 129 ms 416 KB Output is correct
12 Correct 153 ms 344 KB Output is correct
13 Correct 128 ms 344 KB Output is correct
14 Correct 126 ms 344 KB Output is correct
15 Correct 131 ms 344 KB Output is correct
16 Correct 66 ms 344 KB Output is correct
17 Execution timed out 7048 ms 344 KB Time limit exceeded
18 Halted 0 ms 0 KB -

Subtask #2
46.340000001 / 90.0

# Verdict Execution time Memory Grader output
1 Correct 147 ms 344 KB Output is correct (P=0.001, F=15.1, Q=13.2) -> 90.00 points
2 Correct 264 ms 344 KB Output is correct (P=0.005256, F=51.1, Q=58.5) -> 56.99 points
3 Correct 409 ms 344 KB Output is correct (P=0.011546, F=94.9, Q=113.7) -> 50.21 points
4 Correct 667 ms 344 KB Output is correct (P=0.028545, F=191.5, Q=232.5) -> 48.48 points
5 Correct 854 ms 344 KB Output is correct (P=0.039856, F=246.3, Q=300.5) -> 47.87 points
6 Correct 1304 ms 416 KB Output is correct (P=0.068648, F=366.2, Q=445.5) -> 48.23 points
7 Correct 1585 ms 416 KB Output is correct (P=0.104571, F=490.3, Q=595.4) -> 48.45 points
8 Correct 2054 ms 344 KB Output is correct (P=0.158765, F=639.1, Q=777.7) -> 48.19 points
9 Correct 2355 ms 344 KB Output is correct (P=0.2, F=731.4, Q=903.7) -> 46.34 points