Submission #1074559

#	Time	Username	Problem	Language	Result	Execution time	Memory
1074559		GrindMachine	COVID tests (CEOI24_covid)	C++17	95.51 / 100	1851 ms	344 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;
    // vector<ld> dp(n+5,inf2);
    // vector<ll> par(n+5,-1);
    // dp[0] = dp[1] = 0;
    // for(int i = 2; i <= n; ++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);
    //         ld val = 1+all_neg*dp[i-j];
    //         val += (1-all_neg)*(dp[j]+1+(1-all_neg2)*dp[i-j]);
    //         if(val < dp[i]){
    //             dp[i] = val;
    //             par[i] = j;                
    //         }
    //     }
    //     // std::cout << "at N = " << i << " got ev " << dp[i] << " and par is " << par[i] << '\n';
    // }

    // return vector<bool>(n);

    // for(int i = 2; i <= n; ++i){
    //     rep1(j,i-1){
    //         ld all_neg = pow((ld)1-P,j);
    //         ld val = 1+all_neg*dp[i-j];
    //         ld all_neg2 = pow((ld)1-P,i-j);
    //         val += (1-all_neg)*(dp[j]+1+(1-all_neg2)*dp[i-j]);
    //         if(val < dp[i]){
    //             dp[i] = val;
    //             par[i] = j;                
    //         }
    //     }
    // }

    // vector<bool> ans(n);
    // return ans;

    vector<bool> ans(n);
    if(P > 0.25){
        rep(i,n){
            vector<bool> mask(n);
            mask[i] = 1;
            ans[i] = test_students(mask);
        }

        return ans;
    }

    vector<int> pos(n);
    iota(all(pos),0);
 
    mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
    shuffle(all(pos),rng);
 
    auto go = [&](int l, int r, auto &&go){
        if(l > r) return;
 
        vector<bool> mask(n);
        for(int i = l; i <= r; ++i){
            mask[pos[i]] = 1;
        }
    
        int len = r-l+1;
        if(len != n){
            if(!test_students(mask)) return;
        }
 
        if(l == r){
            ans[pos[l]] = 1;
            return;
        }
 
        if(len == 2){
            mask[pos[r]] = 0;
            if(!test_students(mask)){
                ans[pos[r]] = 1;
            }
            else{
                ans[pos[l]] = 1;
                mask[pos[l]] = 0, mask[pos[r]] = 1;
                if(test_students(mask)){
                    ans[pos[r]] = 1;
                }
            }

            return;
        }

        int block_cnt = min(len,3);

        int s1 = len/block_cnt, s2 = ceil2(len,block_cnt);
        int c1 = block_cnt, c2 = len%block_cnt;
        c1 -= c2;
 
        int pos = l;
        vector<pii> nxt;
 
        rep1(iter,block_cnt){
            if(iter <= c1){
                nxt.pb({pos,pos+s1-1});
                pos += s1;
            }
            else{
                nxt.pb({pos,pos+s2-1});
                pos += s2;
            }
        }
            
        assert(pos == r+1);
 
        for(auto [lx,rx] : nxt){
            go(lx,rx,go);
        }        
    };
    
    double eps = 1e-6;
    int B = 0;

    if(abs(P-0.001) <= eps){
        B = n;
    }
    else if(abs(P-0.005256) <= eps){
        B = 150;
    }
    else if(abs(P-0.011546) <= eps){
        B = 60;
    }
    else if(abs(P-0.028545) <= eps){
        B = 20;
    }
    else if(abs(P-0.039856) <= eps){
        B = 16;
    }
    else if(abs(P-0.068648) <= eps){
        B = 8;
    }
    else if(abs(P-0.104571) <= eps){
        B = 8;
    }
    else{
        B = 4;
    }

    auto first_one = [&](int l, int r, auto &&first_one) -> int{
        if(l == r) return l;
        int mid = (l+r) >> 1;
        vector<bool> mask(n);
        for(int i = l; i <= mid; ++i){
            mask[pos[i]] = 1;
        }

        if(test_students(mask)){
            return first_one(l,mid,first_one);
        }
        else{
            return first_one(mid+1,r,first_one);
        }
    };

    for(int i = 0; i < n; ){
        vector<bool> mask(n);
        int r = min(i+B-1,n-1);
        for(int x = i; x <= r; ++x){
            mask[pos[x]] = 1;
        }

        if(!test_students(mask)){
            i = r+1;
            conts;
        }

        int j = first_one(i,r,first_one);
        ans[pos[j]] = 1;
        i = j+1;
    }

    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 'std::vector<bool> find_positive()':
Main.cpp:174:10: warning: variable 'go' set but not used [-Wunused-but-set-variable]
  174 |     auto go = [&](int l, int r, auto &&go){
      |          ^~
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:305:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  305 |     scanf("%d %lf %d", &N, &P, &T);
      |     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
Main.cpp:321:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  321 |         scanf(" %c", &verdict);
      |         ~~~~~^~~~~~~~~~~~~~~~~

• Subtask 0: 0 / 0
• Subtask 1: 10 / 10
• Subtask 2: 85.509999999 / 90