Submission #530241

#	Time	Username	Problem	Language	Result	Execution time	Memory
530241		NachoLibre	Aliens (IOI16_aliens)	C++17	4 / 100	1 ms	296 KiB

aliens

#include <bits/stdc++.h>
#define ll long long
#define ld long double
#define sz(x) ((int)(x).size())
#define all(x) (x).begin(), (x).end()
#define vint vector<int>
using namespace std;
#ifndef x
// #include ".h"
#else
#endif

int n;
vint l, r;

ll p2(ll x) {
	return x * x;
}

ll I(int i) {
	if(r[i] < l[i + 1]) return 0;
	return p2(r[i] - l[i + 1] + 1);
}

ll P(array<ll, 3> p, ll x) {
	return p[0] * x + p[1];
}

bool CW(array<ll, 3> a, array<ll, 3> b, array<ll, 3> c) {
	a[0] = b[0] - a[0];
	a[1] = b[1] - a[1];
	b[0] = c[0] - b[0];
	b[1] = c[1] - b[1];
	return (a[0] * b[1] - b[0] * a[1] > 0);
}

array<ll, 2> dpsol(ll am) {
	vector<array<ll, 2> > dp(n);
	dp[0] = {p2(r[0] - l[0] + 1) + am, 1};
	deque<array<ll, 3> > d;
	int dg = 0;
	for(int i = 0; i < n; ++i) {
		if(i > 0) {
			ll x = -r[i];
			ll c = p2(r[i] + 1) + am;
			while(dg < sz(d) - 1 && P(d[dg + 1], x) < P(d[dg], x)) dg += 1;
			dp[i][0] = P(d[dg], x) + c;
			dp[i][1] = d[dg][2] + 1;
			ll y = p2(r[i] - l[0] + 1) + am;
			if(dp[i][0] > y) {
				dp[i][0] = y;
				dp[i][1] = 1;
			}
		}
		if(i < n - 1) {
			ll a = 2ll * l[i + 1];
			ll b = dp[i][0] - I(i) - 2ll * l[i + 1];
			b += p2(l[i + 1]);
			array<ll, 3> x = {a, b, dp[i][1]};
			while(sz(d) >= 2 && CW(d[sz(d) - 2], d[sz(d) - 1], x)) {
				d.pop_back();
			}
			d.push_back(x);
			dg = min(dg, sz(d) - 1);
		}
	}
	array<ll, 2> x = dp[n - 1];
	x[0] -= x[1] * am;
	return x;
}

ll take_photos(int N, int m, int k, vint R, vint C) {
	n = N;
	vector<int> lg(m, m);
	for(int i = 0; i < n; ++i) {
		array<int, 2> x = {R[i], C[i]};
		if(x[0] > x[1]) swap(x[0], x[1]);
		lg[x[1]] = min(lg[x[1]], x[0]);
	}
	vector<array<int, 2> > v;
	for(int i = 0; i < m; ++i) {
		if(lg[i] == m) continue;
		while(sz(v) && lg[i] <= v.back()[0]) {
			v.pop_back();
		}
		v.push_back({lg[i], i});
	}
	n = sz(v);
	l = r = vint(n);
	for(int i = 0; i < n; ++i) {
		l[i] = v[i][0];
		r[i] = v[i][1];
	}
	ll al = 0, ar = 1e9;
	while(al < ar) {
		ll am = al + ar >> 1;
		if(dpsol(am)[1] > k) al = am + 1;
		else ar = am;
	}
	array<ll, 2> x = dpsol(al);
	// cout << x[1] << " " << al << endl;
	return x[0];
}

#ifdef x
int main() {
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout << "----" << endl;
	cout << take_photos(5, 5, 5, {0, 1, 2, 3, 4}, {0, 1, 2, 3, 4}) << endl;
	cout << take_photos(5, 5, 4, {0, 1, 2, 3, 4}, {0, 1, 2, 3, 4}) << endl;
	cout << take_photos(5, 5, 3, {0, 1, 2, 3, 4}, {0, 1, 2, 3, 4}) << endl;
	cout << take_photos(5, 5, 2, {0, 1, 2, 3, 4}, {0, 1, 2, 3, 4}) << endl;
	cout << take_photos(5, 5, 1, {0, 1, 2, 3, 4}, {0, 1, 2, 3, 4}) << endl;
	cout << "----" << endl;
	cout << take_photos(2, 2, 1, {0, 1}, {0, 1}) << endl;
	cout << take_photos(2, 2, 2, {0, 1}, {0, 1}) << endl;
	cout << take_photos(1, 2, 1, {0}, {1}) << endl;
	cout << "----" << endl;
	cout << take_photos(5, 7, 1, {0, 4, 4, 4, 4}, {3, 4, 6, 5, 6}) << endl;
	cout << take_photos(5, 7, 2, {0, 4, 4, 4, 4}, {3, 4, 6, 5, 6}) << endl;
	cout << take_photos(2, 6, 2, {1, 4}, {4, 1}) << endl;
	return 0;
}
#endif

Compilation message (stderr)

aliens.cpp: In function 'long long int take_photos(int, int, int, std::vector<int>, std::vector<int>)':
aliens.cpp:96:14: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   96 |   ll am = al + ar >> 1;
      |           ~~~^~~~

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