Submission #165201

#	Time	Username	Problem	Language	Result	Execution time	Memory
165201		johutha	Aliens (IOI16_aliens)	C++14	4 / 100	2 ms	376 KiB

aliens

#include "aliens.h"
#include <iostream>
#include <vector>
#include <algorithm>
#include <deque>

#define int long long

using namespace std;

struct line
{
	int a, b;

	int getval(int x)
	{
		return a*x + b;
	}
};

struct convhull
{
	deque<line> hull;

	vector<line> all;

	bool bad(line newl)
	{
		if (hull.size() < 2) return false;
		line snlt = hull[hull.size() - 1];
		line last = hull.back();
		return ((long double) last.b - newl.b) / (newl.a - last.a) <= ((long double) snlt.b - last.b) / (last.a - snlt.a);
	}

	void insert(int a, int b)
	{
		line newl;
		newl.a = a;
		newl.b = b;
		all.push_back(newl);
		while (bad(newl)) hull.pop_back();
		hull.push_back(newl);
	}

	int query(int x)
	{
		if (hull.empty()) return 0;
		while (hull.size() > 1 && hull[0].getval(x) > hull[1].getval(x)) hull.pop_front();
		return hull[0].getval(x);
	}
};

struct dpstruct
{
	int n;
	int k;
	vector<int> l;
	vector<int> r;

	int calc()
	{
		k = min(k, n);
		vector<int> dp(n + 1, 1e17);
		vector<int> olddp(n + 1, 1e17);

		dp[0] = 0;
		olddp[0] = 0;

		for (int ik = 0; ik < k; ik++)
		{
			swap(dp, olddp);

			convhull hull;

			for (int i = 0; i < n; i++)
			{
				int ovlp = 0;
				if (i > 0) ovlp = max(0ll, r[i - 1] - l[i]);
				hull.insert(-2*l[i], olddp[i] + l[i]*l[i] - ovlp*ovlp);
				dp[i + 1] = hull.query(r[i]) + (r[i]*r[i]);
			}
			/*
			for (int j : dp) cerr << j << " ";
			cerr << "\n";*/
			
		}

		return dp[n];
	}
};


int take_photos(signed n, signed m, signed k, vector<signed> r, vector<signed> c)
{
    vector<pair<int,int>> prs;

	for (int i = 0; i < n; i++)
	{
		prs.emplace_back(min(r[i], c[i]), -max(r[i], c[i]));
	}

	sort(prs.begin(), prs.end());

	vector<int> nl;
	vector<int> nr;

	nl.push_back(prs[0].first);
	nr.push_back(-prs[0].second + 1);

	int last = -prs[0].second;

	for (int i = 1; i < n; i++)
	{
		prs[i].second = -prs[i].second;
		if (last < prs[i].second)
		{
			nl.push_back(prs[i].first);
			nr.push_back(prs[i].second + 1);
		}
		last = max(prs[i].second, last);
	}

	dpstruct dps;
	dps.n = nl.size();
	dps.k = k;
	dps.l = nl;
	dps.r = nr;

	return dps.calc();
}

• Subtask 1: 4 / 4
• Subtask 2: 0 / 12
• Subtask 3: 0 / 9
• Subtask 4: 0 / 16
• Subtask 5: 0 / 19
• Subtask 6: 0 / 40