Submission #585270

#	Time	Username	Problem	Language	Result	Execution time	Memory
585270		LucaIlie	Counting Mushrooms (IOI20_mushrooms)	C++17	80.14 / 100	13 ms	392 KiB

mushrooms

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

using namespace std;

int use_machine( vector <int> x );

int count_mushrooms( int n ) {
    bool isA;
    const int k = min( n, max( 3, ((int)sqrt( 4 * n )) * 2 / 2 + 1 ) ), a = 0, b = 1;
    int nrA, pos1, pos2, bs;
    vector <int> s( n ), pos;

    if ( n <= 10 ) {
        nrA = 1;
        for ( int i = 1; i < n; i++ )
            nrA += 1 - use_machine( { 0, i } );
        return nrA;
    }

    s[0] = a;
    s[1] = use_machine( { 0, 1 } ) == 0 ? a : b;
    s[2] = use_machine( { 0, 2 } ) == 0 ? a : b;
    nrA = (s[0] == a) + (s[1] == a) + (s[2] == a);
    if ( nrA == 1 ) {
        isA = false;
        pos1 = 1;
        pos2 = 2;
    } else {
        isA = true;
        pos1 = 0;
        pos2 = (s[1] == a ? 1 : 2);
    }

    for ( int i = 3; i < k; i += 2 ) {
        int r = use_machine( { pos1, i, pos2, i + 1 } );
        if ( r == 0 )
            s[i] = s[i + 1] = (isA ? a : b);
        else if ( r == 1 ) {
            s[i] = (isA ? a : b);
            s[i + 1] = (isA ? b : a);
        } else if ( r == 2 ) {
            s[i] = (isA ? b : a);
            s[i + 1] = (isA ? a : b);
        } else
            s[i] = s[i + 1] = (isA ? b : a);
    }
    for ( int i = 3; i < k; i++ )
        nrA += (s[i] == a);
    if ( nrA > k / 2 ) {
        bs = nrA - 1;
        isA = true;
    } else {
        bs = k - nrA - 1;
        isA = false;
    }
    for ( int i = 0; i < k; i++ ) {
        if ( s[i] == (isA ? a : b) )
            pos.push_back( i );
    }

    for ( int i = k; i < n; i += bs ) {
        int j;
        vector <int> m;

        for ( j = 0; j + 1 < pos.size() && i + j < n; j++ ) {
            m.push_back( pos[j] );
            m.push_back( i + j );
        }
        m.push_back( pos.back() );

        if ( isA )
            nrA += j - use_machine( m ) / 2;
        else
            nrA += use_machine( m ) / 2;
    }

    return nrA;
}

Compilation message (stderr)

mushrooms.cpp: In function 'int count_mushrooms(int)':
mushrooms.cpp:66:28: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   66 |         for ( j = 0; j + 1 < pos.size() && i + j < n; j++ ) {
      |                      ~~~~~~^~~~~~~~~~~~

• Subtask 1: 80.1418 / 100