Submission #522992

#	Time	Username	Problem	Language	Result	Execution time	Memory
522992		dxz05	Counting Mushrooms (IOI20_mushrooms)	C++14	92.62 / 100	11 ms	584 KiB

mushrooms

#include "mushrooms.h"
#include <bits/stdc++.h>

#include <random>

using namespace std;

int count_mushrooms(int n) {
    if (n <= 227){
        int res = 1;
        for (int i = 1; i < n; i++){
            res += use_machine({0, i}) == 0;
        }
        return res;
    }

    vector<int> p(n);
    iota(p.begin(), p.end(), 0);

    shuffle(p.begin() + 1, p.begin() + n, std::mt19937(std::random_device()()));

    vector<int> A = {0}, B;

    int k = 80;

    int i = 1;
    while (i < 3){
        if (use_machine({0, p[i]}) == 0) A.push_back(p[i]); else
            B.push_back(p[i]);
        i++;
    }

    while (max(A.size(), B.size()) < k){
        if (A.size() >= 2){
            int cnt = use_machine({A[0], p[i], A[1], p[i + 1]});
            if (cnt & 2) B.push_back(p[i]); else
                A.push_back(p[i]);
            if (cnt & 1) B.push_back(p[i + 1]); else
                A.push_back(p[i + 1]);
        } else {
            int cnt = use_machine({B[0], p[i], B[1], p[i + 1]});
            if (cnt & 2) A.push_back(p[i]); else
                B.push_back(p[i]);
            if (cnt & 1) A.push_back(p[i + 1]); else
                B.push_back(p[i + 1]);
        }
        i += 2;
    }

    int res = A.size();

    while (i < n){
        vector<int> r;
        if (A.size() > B.size()){
            for (int x : A){
                if (i >= n) break;
                r.push_back(x);
                r.push_back(p[i]);
                i++;
            }

            int cnt = use_machine(r);
            if (cnt & 1) B.push_back(r.back()); else
                A.push_back(r.back());
            res += r.size() / 2 - (cnt + 1) / 2;
        } else {
            for (int x : B){
                if (i >= n) break;
                r.push_back(x);
                r.push_back(p[i]);
                i++;
            }
            int cnt = use_machine(r);
            if (cnt & 1) A.push_back(r.back()); else
                B.push_back(r.back());
            res += (cnt + 1) / 2;
        }
    }

    return res;
}

Compilation message (stderr)

mushrooms.cpp: In function 'int count_mushrooms(int)':
mushrooms.cpp:33:36: warning: comparison of integer expressions of different signedness: 'const long unsigned int' and 'int' [-Wsign-compare]
   33 |     while (max(A.size(), B.size()) < k){
      |            ~~~~~~~~~~~~~~~~~~~~~~~~^~~

• Subtask 1: 92.623 / 100