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QOJ

IDProblemSubmitterResultTimeMemoryLanguageFile sizeSubmit timeJudge time
#242312#7730. Convex CheckerinvadedWA 37ms19216kbC++174.5kb2023-11-07 09:46:082023-11-07 09:46:08

Judging History

你现在查看的是最新测评结果

  • [2024-07-04 19:27:17]
  • hack成功,自动添加数据
  • (/hack/727)
  • [2024-07-04 19:17:30]
  • hack成功,自动添加数据
  • (/hack/726)
  • [2023-11-07 09:46:08]
  • 评测
  • 测评结果:WA
  • 用时:37ms
  • 内存:19216kb
  • [2023-11-07 09:46:08]
  • 提交

answer

#include<bits/stdc++.h>
#ifndef xxx
#define dbg(...) ;
#endif
using namespace std;
//template<class T> ostream &operator<<(ostream &o, const vector <T> &v) { bool f=false; for(T i:v) { f?o<<' ':o; o<<(i); f=true; } return o; }
template<class T> void sort(T &v) { std::sort(v.begin(), v.end()); }
template<class T, class C> void sort(T &v, C c) { std::sort(v.begin(), v.end(), c); }
template<class T> void reverse(T &v) { std::reverse(v.begin(), v.end()); }
template<class T> bool is_sorted(T &v) { return std::is_sorted(v.begin(), v.end()); }
template<class T> inline void _min(T &x, const T &y) { x>y?x=y:x; }
template<class T> inline void _max(T &x, const T &y) { x<y?x=y:x; }
istream &operator>>(istream &i, __int128_t &x) { x=0; short f=1; char c=0; while(!isdigit(c)) { if(c=='-')f=-1; c=i.get(); } while(isdigit(c))x=x*10+c-'0', c=i.get(); x*=f; return i; }
ostream &operator<<(ostream &o, __int128_t x) { if(x==0) { o<<0; return o; } bool f=false; string s; if(x<0)f=true, x=-x; while(x)s+=x%10+'0', x/=10; reverse(s); if(f)o<<'-'; o<<s; return o; }
mt19937 mt(time(0));
typedef double db;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
constexpr int maxn=2e5+5;
constexpr int mod=1e9+7;
constexpr int inf=0x3f3f3f3f;
constexpr ll INF=0x3f3f3f3f3f3f3f3fll;
constexpr double pi=acos(-1.0);
constexpr double eps=1e-9;
struct Point
{
	ll x, y;
	void read()
	{
		cin>>x>>y;
	}
	bool operator<(const Point &p)const
	{
		return x==p.x?y<p.y:x<p.x;
	}
	bool operator==(const Point &p)const
	{
		return x==p.x&&y==p.y;
	}
	friend ostream &operator<<(ostream &o, const Point &p)
	{
		o<<'('<<p.x<<','<<p.y<<')';
		return o;
	}
};
struct Vect
{
	ll x, y;
	Vect() :x(0), y(0) {}
	Vect(Point st, Point ed) :x(ed.x-st.x), y(ed.y-st.y) {}
	ll dot(Vect V)
	{
		return x*V.x+y*V.y;
	}
	ll cross(Vect V)
	{
		return x*V.y-y*V.x;
	}
	ll toLeft(Vect V)
	{
		ll t=cross(V);
		return (t>0)-(t<0);
	}
};
Vect operator-(Point ed, Point st)
{
	return Vect(st, ed);
}
vector<Point> convexHull1(vector<Point> p)
{
	vector<Point> st;
	if(p.empty()) return st;
	sort(p.begin(), p.end());
	const auto check=[](const vector<Point> &st, const Point &u)
	{
		const auto back1=st.back(), back2=*prev(st.end(), 2);
		return (back1-back2).toLeft(u-back1)<=0;
	};
	for(const Point &u:p)
	{
		while(st.size()>1&&check(st, u)) st.pop_back();
		st.push_back(u);
	}
	size_t k=st.size();
	p.pop_back();
	reverse(p.begin(), p.end());
	for(const Point &u:p)
	{
		while(st.size()>k&&check(st, u)) st.pop_back();
		st.push_back(u);
	}
	st.pop_back();
	return st;
}
vector<Point> convexHull2(vector<Point> p)
{
	vector<Point> st;
	if(p.empty()) return st;
	sort(p.begin(), p.end());
	reverse(p);
	const auto check=[](const vector<Point> &st, const Point &u)
	{
		const auto back1=st.back(), back2=*prev(st.end(), 2);
		return (back1-back2).toLeft(u-back1)<=0;
	};
	for(const Point &u:p)
	{
		while(st.size()>1&&check(st, u)) st.pop_back();
		st.push_back(u);
	}
	size_t k=st.size();
	p.pop_back();
	reverse(p.begin(), p.end());
	for(const Point &u:p)
	{
		while(st.size()>k&&check(st, u)) st.pop_back();
		st.push_back(u);
	}
	st.pop_back();
	return st;
}
bool preCheck(const vector<Point> &poly)
{
	int n=poly.size();
	for(int i=0; i<n; i++)
	{
		int u=i;
		int v=(i+1)%n;
		int w=(i+2)%n;
		Vect v1(poly[u], poly[v]);
		Vect v2(poly[v], poly[w]);
		if(v1.toLeft(v2)==0)
		{
			return false;
		}
	}
	return true;
}
bool compare(const vector<Point> &poly, const vector<Point> &convex)
{
	auto it=find(poly.begin(), poly.end(), convex.front());
	if(it==poly.end())return false;
	if(it==poly.begin())it++;
	vector<Point>s1(poly.begin(), it);
	vector<Point>s2(it, poly.end());
	vector<Point>r1=s1;
	vector<Point>r2=s2;
	reverse(r1);
	reverse(r2);
	vector<Point>now1(r1);
	//dbg(r1);
	//dbg(r2);
	now1.insert(now1.end(), r2.begin(), r2.end());
	vector<Point>now2(s2);
	now2.insert(now2.end(), s1.begin(), s1.end());
	//dbg(now1);
	//dbg(now2);
	return now1==convex||now2==convex;
}
int main()//MARK: main
{
#ifndef xxx
	ios::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr);
#endif
	cout<<fixed<<setprecision(10);
	int n;
	cin>>n;
	vector<Point>poly(n);
	for(int i=1; i<=n; i++)
	{
		poly[i-1].read();
	}
	auto convex1=convexHull1(poly);
	auto convex2=convexHull2(poly);
	//dbg(convex1);
	//dbg(convex2);
	bool flag=preCheck(poly)&&(compare(poly, convex1)||compare(poly, convex2));
	cout<<(flag?"Yes":"No")<<'\n';
	return 0;
}

Details

Tip: Click on the bar to expand more detailed information

Test #1:

score: 100
Accepted
time: 0ms
memory: 3688kb

input:

3
0 0
1 0
0 1

output:

Yes

result:

ok answer is YES

Test #2:

score: 0
Accepted
time: 0ms
memory: 3900kb

input:

4
0 0
0 1
1 1
1 0

output:

Yes

result:

ok answer is YES

Test #3:

score: 0
Accepted
time: 0ms
memory: 3676kb

input:

4
0 0
0 3
1 2
1 1

output:

Yes

result:

ok answer is YES

Test #4:

score: 0
Accepted
time: 0ms
memory: 3692kb

input:

3
0 0
0 0
0 0

output:

No

result:

ok answer is NO

Test #5:

score: 0
Accepted
time: 0ms
memory: 3624kb

input:

5
1 0
4 1
0 1
2 0
3 2

output:

No

result:

ok answer is NO

Test #6:

score: 0
Accepted
time: 0ms
memory: 3912kb

input:

5
0 0
1000000000 0
1000000000 500000000
1000000000 1000000000
0 1000000000

output:

No

result:

ok answer is NO

Test #7:

score: 0
Accepted
time: 0ms
memory: 3892kb

input:

5
0 0
1000000000 0
1000000000 499999999
1000000000 1000000000
0 1000000000

output:

No

result:

ok answer is NO

Test #8:

score: 0
Accepted
time: 0ms
memory: 3628kb

input:

5
0 0
999999999 0
1000000000 50000000
999999999 1000000000
0 1000000000

output:

Yes

result:

ok answer is YES

Test #9:

score: 0
Accepted
time: 31ms
memory: 17824kb

input:

128312
5578014 410408218
5585076 410404717
5588011 410403262
5588473 410403033
5589740 410402405
5593295 410400643
5593751 410400417
5597248 410398684
5598935 410397848
5600618 410397014
5605185 410394751
5610514 410392111
5614281 410390245
5617263 410388768
5621142 410386847
5630840 410382045
56310...

output:

Yes

result:

ok answer is YES

Test #10:

score: -100
Wrong Answer
time: 37ms
memory: 19216kb

input:

128086
149550602 509469827
149551059 509465022
149551336 509462107
149551964 509455497
149552572 509449094
149553350 509440895
149553656 509437667
149554161 509432339
149554254 509431357
149554545 509428284
149555017 509423299
149555366 509419611
149555842 509414580
149556382 509408867
149556564 509...

output:

No

result:

wrong answer expected YES, found NO