Submission #306915

#	Time	Username	Problem	Language	Result	Execution time	Memory
306915		baluteshih	Counting Mushrooms (IOI20_mushrooms)	C++14	92.62 / 100	13 ms	512 KiB

mushrooms

#include "mushrooms.h"
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
#define X first
#define Y second
#define ALL(v) v.begin(),v.end()
#define pb push_back
#define SZ(a) ((int)a.size())

const int K=75;

int count_mushrooms(int n)
{
    if(n==2)
        return 2-use_machine({0,1});
    srand(time(NULL));
    int ans=0;
    vector<int> num(n-1,0);
	vector<int> a(1,0),b;
    for(int i=0;i+1<n;++i)
        num[i]=i+1;
    random_shuffle(ALL(num));
    for(int i=0;i<2;++i)
        if(use_machine({0,num[i]})==0)
            a.pb(num[i]);
        else
            b.pb(num[i]);
    for(int i=2,j=0;i+1<SZ(num)&&j<K;i+=2,++j)
    {
        if(SZ(a)>=2)
        {
            int x=use_machine({a[0],num[i],a[1],num[i+1]});
            if(x==0)
                a.pb(num[i]),a.pb(num[i+1]);
            else if(x==1)
                a.pb(num[i]),b.pb(num[i+1]);
            else if(x==2)
                a.pb(num[i+1]),b.pb(num[i]);
            else
                b.pb(num[i]),b.pb(num[i+1]);
        }
        else
        {
            int x=use_machine({b[0],num[i],b[1],num[i+1]});
            if(x==0)
                b.pb(num[i]),b.pb(num[i+1]);
            else if(x==1)
                b.pb(num[i]),a.pb(num[i+1]);
            else if(x==2)
                b.pb(num[i+1]),a.pb(num[i]);
            else
                a.pb(num[i]),a.pb(num[i+1]);
        }
    }
    if(SZ(num)<=2+2*K)
    {
        if((n&1)^1)
        {
            if(use_machine({0,num.back()})==0)
                a.pb(num.back());
            else
                b.pb(num.back());
        }
        return SZ(a);
    }
    ans=SZ(a);
    int nw=2+2*K;
    while(nw+max(SZ(a),SZ(b))<=SZ(num))
    {
        if(SZ(a)>=SZ(b))
        {
            int q=SZ(a);
            vector<int> tmp;
            for(int j=0;j<q;++j)
                tmp.pb(a[j]),tmp.pb(num[nw+j]);
            int x=use_machine(tmp);
            if(x&1)
                --x,b.pb(num[nw+q-1]);
            else
                ++ans,a.pb(num[nw+q-1]);
            ans+=((q-1)*2-x)/2;
            nw+=q;
        }
        else
        {
            int q=SZ(b);
            vector<int> tmp;
            for(int j=0;j<q;++j)
                tmp.pb(b[j]),tmp.pb(num[nw+j]);
            int x=use_machine(tmp);
            if(x&1)
                ++ans,--x,a.pb(num[nw+q-1]);
            else
                b.pb(num[nw+q-1]);
            ans+=x/2;
            nw+=q;
        }
    }
    if(nw<SZ(num))
    {
        if(SZ(a)>=SZ(b))
        {
            vector<int> tmp;
            for(int j=0;nw+j<SZ(num);++j)
                tmp.pb(a[j]),tmp.pb(num[nw+j]);
            tmp.pb(a.back());
            int x=use_machine(tmp);
            ans+=((SZ(num)-nw)*2-x)/2;
        }
        else
        {
            vector<int> tmp;
            for(int j=0;nw+j<SZ(num);++j)
                tmp.pb(b[j]),tmp.pb(num[nw+j]);
            tmp.pb(b.back());
            int x=use_machine(tmp);
            ans+=x/2;
        }
    }
    return ans;
}

• Subtask 1: 92.623 / 100