Submission #549172

#	Time	Username	Problem	Language	Result	Execution time	Memory
549172		kingfran1907	SIR (COI15_sir)	C++14	100 / 100	159 ms	12348 KiB

sir

#include <bits/stdc++.h>
#define X first
#define Y second

using namespace std;
typedef long long llint;

const int maxn = 3e5+10;
const int base = 31337;
const int mod = 1e9+7;
const int inf = 0x3f3f3f3f;
const int logo = 20;
const int off = 1 << logo;
const int treesiz = off << 1;

int n, m;
pair<int, int> niz[maxn], ss[maxn];
vector< int > hul, hul2;
vector< pair<int, int> > hull;
bool bio[maxn];

llint ccw(pair<int, int> a, pair<int, int> b, pair<int, int> c) {
	return (llint)a.X * (b.Y - c.Y) + (llint)b.X * (c.Y - a.Y) + (llint)c.X * (a.Y - b.Y);
} 

int main() {
	scanf("%d", &n);
	for (int i = 0; i < n; i++) {
		int x, y;
		scanf("%d%d", &x, &y);
		niz[i] = {x, y};
	}

	scanf("%d", &m);
	for (int i = 0; i < m; i++) {
		int x, y;
		scanf("%d%d", &x, &y);
		ss[i] = {x, y};
	}

	sort(ss, ss + m);
	for (int i = 0; i < m; i++) {
		while (hul.size() >= 2 && ccw(ss[hul[hul.size() - 2]], ss[hul.back()], ss[i]) >= 0) 
			hul.pop_back();
		hul.push_back(i);
	}

	//printf("debug: \n");
	//for (int i = 0; i < hul.size(); i++) {
	//	printf("%d %d\n", ss[hul[i]].X, ss[hul[i]].Y);
	//}

	reverse(ss, ss + m);
	for (int i = 0; i < m; i++) {
		while (hul2.size() >= 2 && ccw(ss[hul2[hul2.size() - 2]], ss[hul2.back()], ss[i]) >= 0)
			hul2.pop_back();
		hul2.push_back(i);
	}

	//printf("debug: \n");
	//for (int i = 0; i < hul2.size(); i++) {
	//	printf("%d %d\n", ss[hul2[i]].X, ss[hul2[i]].Y);
	//}

	reverse(ss, ss + m);
	//for (int tren : hul2) hul.push_back(m - 1 - tren);
	//memset(bio, false, sizeof bio);
	for (int i = 0; i < hul.size(); i++) {
		hull.push_back(ss[hul[i]]);
	}
	for (int i = 1; i < hul2.size() - 1; i++)  {
		hull.push_back(ss[m - 1 - hul2[i]]);
	}
	reverse(hull.begin(), hull.end());

	int ptrh = 0;
	int siz = hull.size();
	for (int i = 0; i < siz; i++) {
		if (ccw(niz[0], hull[ptrh], hull[i]) < 0) ptrh = i;
	}

	for (int i = 0; i < siz; i++) {
		assert(ccw(hull[i], hull[(i + 1) % siz], hull[(i + 2) % siz]) >= 0);
	}

	llint sol = 0;
	int ptr = 0;
	llint tren = 0;
	for (int i = 0; i < n; i++) {
		while (siz > 1 && ccw(niz[i], hull[ptrh], hull[(ptrh + 1) % siz]) <= 0) {
			ptrh++;
			if (ptrh == siz) ptrh = 0;
		}

		while (true) {
			tren += abs(ccw(niz[i], niz[ptr], niz[(ptr + 1) % n]));
			bool flag = ccw(niz[i], hull[ptrh], niz[(ptr + 1) % n]) < 0;

			//if (flag) printf("%d --> %d (%lld)\n", i, ptr, tren);
			if (flag) sol = max(sol, tren), ptr++, ptr %= n;
			else {
				tren -= abs(ccw(niz[i], niz[ptr], niz[(ptr + 1) % n]));
				break;
			}
		}
		tren -= abs(ccw(niz[i], niz[(i + 1) % n], niz[ptr]));
	}
	printf("%lld\n", sol);
	return 0;
}

Compilation message (stderr)

sir.cpp: In function 'int main()':
sir.cpp:68:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   68 |  for (int i = 0; i < hul.size(); i++) {
      |                  ~~^~~~~~~~~~~~
sir.cpp:71:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   71 |  for (int i = 1; i < hul2.size() - 1; i++)  {
      |                  ~~^~~~~~~~~~~~~~~~~
sir.cpp:27:7: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   27 |  scanf("%d", &n);
      |  ~~~~~^~~~~~~~~~
sir.cpp:30:8: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   30 |   scanf("%d%d", &x, &y);
      |   ~~~~~^~~~~~~~~~~~~~~~
sir.cpp:34:7: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   34 |  scanf("%d", &m);
      |  ~~~~~^~~~~~~~~~
sir.cpp:37:8: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   37 |   scanf("%d%d", &x, &y);
      |   ~~~~~^~~~~~~~~~~~~~~~

• Subtask 1: 12 / 12
• Subtask 2: 39 / 39
• Subtask 3: 49 / 49