Submission #592614

#	Time	Username	Problem	Language	Result	Execution time	Memory
592614		hltk	The Big Prize (IOI17_prize)	C++17	100 / 100	48 ms	1872 KiB

prize

#include "prize.h"

#include <bits/stdc++.h>

using namespace std;

using pii = pair<int, int>;

vector<pii> C;

pii m_ask(int i) {
	if (C[i].first != -1) return C[i];
	auto a = ask(i);
	return C[i] = {a[0], a[1]};
}


// 1, 2, 5, 26, 677

int find_best(int n) {
	C.assign(n, {-1, -1});
	if (n <= 7000) {
		for (int i = 0; i < n; ++i) {
			auto [a, b] = m_ask(i);
			if (a + b == 0) {
				return i;
			}
		}
		throw;
	}
	int B = n / 500;
	vector<int> pt;
	for (int i = 0; i < n; i += B) {
		pt.push_back(i);
	}
	int t = 0;
	for (int i : pt) {
		auto [a, b] = m_ask(i);
		t = max(t, a + b);
	}
	auto check = [&](int i) {
		auto [a, b] = m_ask(i);
		return a + b != t;
	};
	int jt = 0;
	for (int i = 0; i < n; ++i) {
		if (check(i)) {
			auto [a, b] = m_ask(i);
			if (a + b == 0) return i;
		} else {
			auto same = [&](int j) {
				return !check(j) && m_ask(j).second == m_ask(i).second;
			};
			int st = i, ed = n - 1;
			while (pt[jt] <= i) ++jt;
			for (int it = jt; it < (int) pt.size(); ++it) {
				int j = pt[it];
				if (same(j)) {
					st = j;
				} else {
					ed = j;
					break;
				}
			}
			while (st < ed) {
				int m = (st + ed) / 2;
				if (!same(m)) ed = m;
				else st = m + 1;
			}
			i = st - 1;
			assert(check(st));
		}
	}
}

Compilation message (stderr)

prize.cpp: In function 'int find_best(int)':
prize.cpp:32:14: warning: control reaches end of non-void function [-Wreturn-type]
   32 |  vector<int> pt;
      |              ^~

• Subtask 1: 20 / 20
• Subtask 2: 80 / 80