Submission #298954

#	Time	Username	Problem	Language	Result	Execution time	Memory
298954		SeDunion	Aliens (IOI16_aliens)	C++17	41 / 100	485 ms	2944 KiB

aliens

#include "aliens.h"
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;

const int N = 4e3 + 123;
const int K = 4e3 + 123;
const ll INF = 1e18;

ll x[N], y[N];

ll sq (ll x) { return x * x; }

struct line {
	ll k, b;
	ll f (ll x) {
		return k * x + b;
	}
};

ld inter (line a, line b) {
	return ld(b.b - a.b) / ld(a.k - b.k);
}

struct cht {
	vector<line> v;
	void add (line a) {
		while (v.size() > 1 && inter (v.back(), v[v.size() - 2]) > inter (v[v.size() - 2], a)) {
			v.pop_back();
		}
		v.push_back (a);
	}
	ll get (ll x) {
		if (0) {
			ll ans = -INF;
			for (auto l : v) ans = max (ans, l.f(x));
			return ans;
			assert (0);
		}

		if (v.empty()) return -INF;
		int l = 0, r = int(v.size()) - 2;
		ll ans = v.back().f(x);
		while (l <= r) {
			int m = (l + r) >> 1;
			ans = max (ans, v[m].f(x));
			if (inter (v[m], v[m + 1]) < x) {
				l = m + 1;
			} else {
				r = m - 1;
			}
		}
		if (l < (int)v.size())
			ans = max (ans, v[l].f(x));
		if (r >= 0)
			ans = max (ans, v[r].f(x));
		return ans;		
	}
};

ll calc (int n, int m, int k) {
	k = min (n, k);
	vector<ll> dp(n + 1, INF), new_dp;
	for (int i = 1 ; i <= n ; ++ i) {
		dp[i] = sq(y[i] - x[1] + 1);
//		cout << dp[i] << " ";
	}
//	cout << "\n";
	for (int _ = 2 ; _ <= k ; ++ _) {
		new_dp = vector<ll>(n + 1, INF);
		cht ok;
		for (int i = 1 ; i <= n ; ++ i) {
			if (i >= _)
				ok.add ({2 * x[i], -dp[i - 1] - sq(x[i]) + 2 * x[i] - 1 + sq(max(0ll,y[i-1]-x[i]+1))});
			if (i >= _)
				new_dp[i] = sq(y[i]) + 2 * y[i] - ok.get (y[i]);
//			cout << new_dp[i] << " ";
		}
//		cout << "\n";
		swap (dp, new_dp);
	}
	return dp[n];
}

ll take_photos(int n, int m, int k, vector<int> r, vector<int> c) {
	vector<pair<int,int>> a(n);
	for (int i = 0 ; i < n ; ++ i) {
		if (r[i] > c[i]) swap (r[i], c[i]);
		a[i] = {r[i], c[i]};
	}
	sort (a.begin(), a.end());
	int n_ = 0;
	for (int i = 0, ymx = -1 ; i < n ; ++ i) {
		bool rm = false;
		//cout << a[i].first << " " << a[i].second << " a[i]\n";
		if (i + 1 < n && a[i].first == a[i + 1].first) {
			rm = true;
		}
		if (a[i].second <= ymx) {
			rm = true;
		}
		if (!rm) {
			++n_;
			x[n_] = a[i].first;
			y[n_] = a[i].second;
			//cout << x[n_] << " " << y[n_] << " {x,y}\n";
		}
		if (i + 1 > n || a[i].first != a[i + 1].first)
			ymx = max (ymx, a[i].second);
	}
	n = n_;
	return calc (n, m, k);
}

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