Submission #1160632

#	Time	Username	Problem	Language	Result	Execution time	Memory
1160632		Cyanmond	COVID tests (CEOI24_covid)	C++20	100 / 100	764 ms	444 KiB

Main

#include <bits/stdc++.h>
#define AOTSUKI

using namespace std;
constexpr bool isMultiCase = 1;

// #include "angel/math/modint.hpp"

using ll = long long;
template <class T> constexpr int len(const T &c) {
    return int(std::ssize(c));
}
template <class T> using V = vector<T>;
template <class T> using RevPq = priority_queue<T, vector<T>, greater<T>>;
constexpr char eoln = '\n';
#define L(i, l, r) for (int i = (l); i < (r); ++i)
#define R(i, l, r) for (int i = (r) - 1; i >= (l); --i)
#define ALL(x) (x).begin(), (x).end()
#define fi first
#define se second

#include <cassert>
#include <cstdio>
#include <string>
#include <vector>

/// 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';
}

/// 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.

using Float = long double;
V<Float> opt;
V<Float> opos;

void init() {
    opt.resize(N + 2, 1ll << 60);
    opos.resize(N + 2, 0);
    opt[0] = 0;
    opt[1] = 0;
    L(i, 2, N + 2) {
        // split
        Float ngn = pow(1 - P, i);
        Float amin = 0;
        L(j, 1, i) {
            Float score = 1;
            Float up = ((1 - pow(1 - P, j)) / (1 - ngn));
            // cerr << i << ' ' << j << ' ' << up << endl;
            score += opt[j] * up;
            // 見つからなかったら
            score += opt[i - j] * (1 - up);

            if (score < opt[i]) {
                opt[i] = score;
                amin = j;
            }
        }
        opos[i] = amin;
    }
}

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

    L(l, -1, N) {
        int r = N;
        Float pex = 1 - pow(1 - P, N - l - 1);
        if (1 + pex * opt[r - l] < opt[r - l]) {
            V<bool> mask(N);
            L(i, l + 1, N) mask[i] = true;
            auto res = test_students(mask);
            if (not res) break;
        }

        while (r - l > 1) {
            int m = l + 1 + opos[r - l];
            // cerr << m << endl;
            V<bool> mask(N);
            L(i, l + 1, m) mask[i] = true;
            auto res = test_students(mask);

            if (res) r = m - 1;
            else l = m - 1;
        }
        if (r == N) break;
        answer[r] = true;
    }

    return answer;
}

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

    // You may perform any extra initialization here.
    P = min(P, 0.2);
    P = max(P, 0.001);
    init();
    /*
    for (auto e : opt) cerr << e << ' ';
    cerr << endl;
    for (auto e : opos) cerr << e << ' ';
    cerr << 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:123:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  123 |     scanf("%d %lf %d", &N, &P, &T);
      |     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
Main.cpp:147:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  147 |         scanf(" %c", &verdict);
      |         ~~~~~^~~~~~~~~~~~~~~~~

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