Submission #1364002

#	Time	Username	Problem	Language	Result	Execution time	Memory
1364002		Aviansh	COVID tests (CEOI24_covid)	C++20	91.41 / 100	592 ms	440 KiB

Main

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

// 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.

int calcsize(double prob){
    double ans = (1.0)/prob;
    ans/=1.8;
    if(rand()%2){
        return floor(ans);
    }
    return ceil(ans);
}

vector<int>ans;

bool test(int l, int r){
    vector<bool>quer(N);
    for(int i = l;i<=r;i++){
        auto it = lower_bound(ans.begin(),ans.end(),i);
        if(it!=ans.end()){
            if((*it)==i)
                continue;
        }
        quer[i]=1;
    }
    return test_students(quer);
}

int solve(int l, int r){
    //assume there is atleast one here
    if(l==r){
        return l;
    }
    int mid = (l+r)/2;
    if(test(l,mid)){
        return solve(l,mid);
    }
    else{
        return solve(mid+1,r);
    }
}

std::vector<bool> find_positive() {
    std::vector<bool> answer(N);
    if(P==0){
        return answer;
    }
    ans.clear();
    int siz = calcsize(P);
    int lef = 0;
    while(lef<N){
        int rig = lef+siz;
        rig=min(rig,N-1);
        if(test(lef,rig)){
            int nx = solve(lef,rig);
            lef=nx+1;
            answer[nx]=1;
            ans.push_back(nx);
        }
        else{
            lef=rig+1;
        }
    }
    return answer;
}

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

    // You may perform any extra initialization here.

    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: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 'int main()':
Main.cpp:107:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  107 |     scanf("%d %lf %d", &N, &P, &T);
      |     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
Main.cpp:123:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  123 |         scanf(" %c", &verdict);
      |         ~~~~~^~~~~~~~~~~~~~~~~

• Subtask 0: 0 / 0
• Subtask 1: 10 / 10
• Subtask 2: 81.41 / 90