Submission #1006246

#	Time	Username	Problem	Language	Result	Execution time	Memory
1006246		thinknoexit	Counting Mushrooms (IOI20_mushrooms)	C++17	86.59 / 100	6 ms	600 KiB

mushrooms

#include "mushrooms.h"
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int n;
int count_mushrooms(int N) {
	n = N;
	if (n <= 900) {
		vector<int> A, B;
		A.push_back(0);
		int p;
		for (p = 2;p < n;p += 2) {
			if (A.size() < 2 && B.size() < 2) {
				int v = use_machine({ p - 1, 0, p });
				if (v == 0) {
					A.push_back(p);
					A.push_back(p - 1);
				}
				else if (v == 2) {
					B.push_back(p);
					B.push_back(p - 1);
				}
				else {
					if (use_machine({ 0, p })) B.push_back(p), A.push_back(p - 1);
					else B.push_back(p - 1), A.push_back(p);
				}
			}
			else if (A.size() >= 2) {
				int v = use_machine({ A[0], p - 1, A[1], p });
				if (v & 1) B.push_back(p);
				else A.push_back(p);
				if (v & 2) B.push_back(p - 1);
				else A.push_back(p - 1);
			}
			else {
				int v = use_machine({ B[0], p - 1, B[1], p });
				if (!(v & 1)) B.push_back(p);
				else A.push_back(p);
				if (!(v & 2)) B.push_back(p - 1);
				else A.push_back(p - 1);
			}
		}
		p--;
		if (p == n - 1) {
			if (use_machine({ 0, p })) B.push_back(p);
			else A.push_back(p);
		}
		return (int)A.size();
	}
	int sq = 150;
	vector<int> A, B;
	A.push_back(0);
	int p;
	for (p = 2;p < n && (int)A.size() < sq && (int)B.size() < sq;p += 2) {
		if (A.size() < 2 && B.size() < 2) {
			int v = use_machine({ p - 1, 0, p });
			if (v == 0) {
				A.push_back(p);
				A.push_back(p - 1);
			}
			else if (v == 2) {
				B.push_back(p);
				B.push_back(p - 1);
			}
			else {
				if (use_machine({ 0, p })) B.push_back(p), A.push_back(p - 1);
				else B.push_back(p - 1), A.push_back(p);
			}
		}
		else if (A.size() >= 2) {
			int v = use_machine({ A[0], p - 1, A[1], p });
			if (v & 1) B.push_back(p);
			else A.push_back(p);
			if (v & 2) B.push_back(p - 1);
			else A.push_back(p - 1);
		}
		else {
			int v = use_machine({ B[0], p - 1, B[1], p });
			if (!(v & 1)) B.push_back(p);
			else A.push_back(p);
			if (!(v & 2)) B.push_back(p - 1);
			else A.push_back(p - 1);
		}
	}
	p--;
	// count A from p -> n - 1
	int ans = A.size();
	while (p < n) {
		int j;
		if (A.size() > B.size()) {
			int sz = A.size();
			vector<int> Q;
			for (j = p;j < min(n, p + sz);j++) {
				Q.push_back(j);
				Q.push_back(A[j - p]);
			}
			int v = use_machine(Q);
			int s = Q.size();
			ans += (s - v) / 2;
			if (!(v & 1)) A.push_back(p);
			else B.push_back(p);
		}
		else {
			int sz = B.size();
			vector<int> Q;
			for (j = p;j < min(n, p + sz);j++) {
				Q.push_back(j);
				Q.push_back(B[j - p]);
			}
			int v = use_machine(Q);
			ans += (v + 1) / 2;
			if (v & 1) A.push_back(p);
			else B.push_back(p);
		}
		p = j;
	}
	return ans;
}

• Subtask 1: 86.59 / 100