Submission #410745

#	Time	Username	Problem	Language	Result	Execution time	Memory
410745		SeDunion	Counting Mushrooms (IOI20_mushrooms)	C++17	56.93 / 100	14 ms	592 KiB

mushrooms

#include "mushrooms.h"
#include<bits/stdc++.h>
using namespace std;

int K;

int askline(int l, int r) {
	vector<int>toquest;
	for (int i = l ; i <= r ; ++ i) toquest.emplace_back(i);
	return use_machine(toquest);
}

int fnd(vector<int>unk, vector<int>giv) {
	int ret = 0;
	int cnt = (int)giv.size();
	assert(cnt != 0);
	int tfn = (int)unk.size();
	for (int i = 0 ; i < tfn ; i += cnt) {
		int l = i, r = min(tfn - 1, i + cnt - 1);
		vector<int>crop;
		for (int j = l ; j <= r ; ++ j) {
			crop.emplace_back(unk[j]);
			crop.emplace_back(giv[j-l]);
		}
		ret += (use_machine(crop) + 1) / 2;
	}
	return ret;
}

int count_mushrooms(int n) {
	int cur = -1;
	for (int k = 1 ; k <= n ; ++ k) {
		int asked = k;
		int ch = (asked + 1) / 2;
		int others = n - asked;
		int total = (others + ch - 1) / ch + asked;
		if (cur == -1 || cur > total) {
			cur = total;
			K = k;
		}
	}
	vector<int>who(n, 2); // 0 -> A, 1 -> B, 2 -> unknown
	who[0] = 0;
	for (int p = 0 ; p < K - 1 ; ++ p) {
		int ret = askline(p, p + 1);
		who[p + 1] = who[p] ^ (ret & 1);
	}
	array<vector<int>, 3>vecs;
	for (int i = 0 ; i < n ; ++ i) {
		vecs[who[i]].emplace_back(i);
	}
	if (vecs[0].size() > vecs[1].size()) { // we will search the number of bs
		return n - fnd(vecs[2], vecs[0]) - vecs[1].size();
	} else { // the number of as
		return fnd(vecs[2], vecs[1]) + vecs[0].size();
	}
}

• Subtask 1: 56.927 / 100