Submission #1074644

#	Time	Username	Problem	Language	Result	Execution time	Memory
1074644		GrindMachine	COVID tests (CEOI24_covid)	C++17	10 / 100	7039 ms	1104 KiB

Main

#include <bits/stdc++.h>
using namespace std;
 
typedef long long int ll;
typedef long double ld;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
 
#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL)
#define pb push_back
#define endl '\n'
#define conts continue
#define sz(a) (int)a.size()
#define ff first
#define ss second
#define all(a) a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()
#define ceil2(x,y) ((x+y-1)/(y))
 
#define rep(i,n) for(int i = 0; i < n; ++i)
#define rep1(i,n) for(int i = 1; i <= n; ++i)
#define rev(i,s,e) for(int i = s; i >= e; --i)
#define trav(i,a) for(auto &i : a)
 
template<typename T>
void amin(T &x, T y){
    x = min(x,y);
}
 
template<typename T>
void amax(T &x, T y){
    x = max(x,y);
}
 
template<typename A,typename B>
string to_string(pair<A,B> p);
 
string to_string(const string &s){
    return "'"+s+"'";
}
 
string to_string(const char* s){
    return to_string((string)s);
}
 
string to_string(bool b){
    return b?"true":"false";
}
 
template<typename A>
string to_string(A v){
    string res = "{";
    trav(x,v){
        res += to_string(x)+",";
    }
    if(res.back() == ',') res.pop_back();
    res += "}";
    return res;
}
 
template<typename A,typename B>
string to_string(pair<A,B> p){
    return "("+to_string(p.ff)+","+to_string(p.ss)+")";
}
 
#define debug(x) cout << "[" << #x << "]: "; cout << to_string(x) << endl

/*

refs:
edi

*/ 

const int MOD = 1e9 + 7;
const int NN = 1e5 + 5;
const int inf1 = 1e9 + 5;
const ll inf2 = (ll)1e18 + 5;

bool dbg = false;

/// 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) {
    if(dbg) return 'P';

    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.
std::vector<bool> find_positive() {
    // std::vector<bool> answer(N);
    // return answer;
    
    int n = N;
    std::vector<ld> dp(n+5,1e9);
    std::vector<ld> dp2(n+5,1e9);
    std::vector<int> par(n+5,-1);
    std::vector<int> par2(n+5,-1);
    dp[0] = dp[1] = 0;
    dp2[0] = 0, dp2[1] = 1;
    par2[1] = 1;
    for(int i = 2; i <= n; ++i){
        ld tot_neg = powl((ld)1-P, i);
        for(int j = 1; j < i; j++){
            ld all_neg2 = powl((ld)1-P,i-j);
            ld all_neg = powl((ld)1-P,j) * (1 - all_neg2) / (1 - tot_neg);
            ld val = 1+all_neg*dp[i-j];
            val += (1-all_neg)*(dp[j]+dp2[i-j]);
            if(val < dp[i]){
                dp[i] = val;
                par[i] = j;                
            }
        }
        for(int j = 1; j <= i; j++){
            ld all_neg = powl((ld)1-P,j);
            ld val = 1+(1-all_neg)*dp[j]+dp2[i-j];
            if(val < dp2[i]){
                dp2[i] = val;
                par2[i] = j;                
            }
        }
        // std::cout << "at N = " << i << " got ev " << dp[i] << " and par is " << par[i] << '\n';
        // std::cout << "at N = " << i << " got ev " << dp2[i] << " and par is " << par2[i] << '\n';
    }

    vector<bool> ans(n);

    auto go = [&](int l, int r, int t, auto &&go) -> void{
        // t = 0: positive not guaranteed (use dp2)
        // t = 1: at least 1 positive (use dp)
        if(l > r) return;

        int len = r-l+1;

        if(t){
            if(len == 1){
                ans[l] = 1;
                return;
            }

            int j = par[len];
            vector<bool> mask(n);
            for(int k = l; k < l+j; ++k){
                mask[k] = 1;
            }

            if(!test_students(mask)){
                // no positive on left
                // at least 1 positive on right
                go(l+j,r,1,go);
            }
            else{
                // at least 1 positive on left
                // not guaranteed on right
                go(l,l+j-1,1,go);
                go(l+j,r,0,go);
            }
        }
        else{
            if(len == 1){
                vector<bool> mask(n);
                mask[l] = 1;
                ans[l] = test_students(mask);
                return;
            }

            int j = par2[len];
            vector<bool> mask(n);
            for(int k = l; k < l+j; ++k){
                mask[k] = 1;
            }

            if(!test_students(mask)){
                // no positive on left
                // not guaranteed on right
                go(l+j,r,0,go);
            }
            else{
                // positive on left
                // not guaranteed on right
                go(l,l+j-1,1,go);
                go(l+j,r,0,go);
            }
        }
    };

    go(0,n-1,0,go);
    return ans;
}
 
int main() {
    #ifdef LOCAL
        dbg = true;
    #endif

    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:107:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  107 |     scanf(" %c", &answer);
      |     ~~~~~^~~~~~~~~~~~~~~~
Main.cpp: In function 'int main()':
Main.cpp:224:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  224 |     scanf("%d %lf %d", &N, &P, &T);
      |     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
Main.cpp:240:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  240 |         scanf(" %c", &verdict);
      |         ~~~~~^~~~~~~~~~~~~~~~~

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