Submission #1073637

#	Time	Username	Problem	Language	Result	Execution time	Memory
1073637		ProtonDecay314	COVID tests (CEOI24_covid)	C++17	0 / 100	1 ms	344 KiB

Main

// AM + DG
#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef vector<ll> vll;
typedef vector<vll> vvll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<ll, ll> pll;
typedef vector<pll> vpll;
typedef pair<int, int> pi;
typedef vector<pi> vpi;
typedef vector<bool> vb;
typedef vector<double> vd;
#define fi first
#define se second
#define IOS cin.tie(nullptr); cout.tie(nullptr); ios_base::sync_with_stdio(false)
#define pb push_back
#define INF(dtype) numeric_limits<dtype>::max()
#define NINF(dtype) numeric_limits<dtype>::min()

/// You may use:

// The number of students
int N;

// The probability any given student is positive
double P;

// The size of the set that maximizes entropy/"surprise"
// int k;
vd dp;
vi dpi;

// 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 solve(int l, int r, vb& answer) {
    vb mask(N, false);

    int sz = r - l + 1;

    if(l == r) {
        mask[l] = true;
        answer[l] = test_students(mask);
        // answer[l] = true;
        mask[l] = false;
    } else {
        int lsz = dpi[sz];
        if(lsz > 0) {
            for(int i = l; i < l + lsz; i++) mask[i] = true;
            bool res = test_students(mask);
            for(int i = l; i < l + lsz; i++) mask[i] = false;

            int m = l + lsz - 1;
            if(res) {
                if(lsz == 1) {
                    answer[l] = true;
                } else {
                    solve(l, m, answer);
                }
            }
            else {
                for(int i = l; i < l + lsz; i++) {
                    answer[i] = false;
                }
            }
            solve(m + 1, r, answer);
        } else {
            // brute force

            for(int i = l; i <= r; i++) {
                mask[i] = true;
                answer[i] = test_students(mask);
                mask[i] = false;
            }
        }
    }
}

std::vector<bool> find_positive() {
    std::vector<bool> answer(N);

    solve(0, N - 1, answer);

    return answer;
}

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

    // You may perform any extra initialization here.

    // Compute size of set that maximizes "surprisal"
    // k = max((int)lround(-1.0 / log2(1.0 - P)), 1);
    dp = vd(N + 1);
    dpi = vi(N + 1);
    
    dp[0] = 0.0;
    dp[1] = 1.0;
    dpi[0] = 0;
    dpi[1] = 0;

    double onemp = 1.0 - P;

    for(int i = 2; i <= N; i++) {
        double min_ans = INF(double);

        int min_ind = 1;

        for(int j = 1; j < i; j++) {
            double onemppwk = pow(onemp, j);
            double cand = 1.0 + dp[i - j] + (1.0 - onemppwk) * dp[j];
            // double cand = 


            if(cand < min_ans) {
                min_ans = cand;
                min_ind = j;
            }
        }

        dp[i] = min_ans;
        dpi[i] = (T == 1 ? 1 : min_ind);

        cout << i << " " << dp[i] << " " << dpi[i] << endl;
    }

    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:50:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   50 |     scanf(" %c", &answer);
      |     ~~~~~^~~~~~~~~~~~~~~~
Main.cpp: In function 'int main()':
Main.cpp:114:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  114 |     scanf("%d %lf %d", &N, &P, &T);
      |     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
Main.cpp:165:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  165 |         scanf(" %c", &verdict);
      |         ~~~~~^~~~~~~~~~~~~~~~~

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