Submission #950284

#	Time	Username	Problem	Language	Result	Execution time	Memory
950284		Baytoro	Planine (COCI21_planine)	C++17	0 / 110	7 ms	3160 KiB

Main

#include <bits/stdc++.h>
using namespace std;
#define ios ios::sync_with_stdio(false); cin.tie(NULL);
#define pb push_back
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define fr first
#define sc second
#define mp make_pair
#define ll long long
#define double long double
const ll INF=1e18,N=1e6+5;
bool cmp(pair<double,double> a, pair<double,double> b){
	if(a.sc==b.sc) return a.fr<b.fr;
	return a.sc<b.sc;
}
int x[N],y[N];
double slope(int a, int b){
	return (y[b]-y[a])/(x[b]-x[a]+0.0);
}

int cross(int A, int B, int C){
	pair<int,int> a=mp(x[A],y[A]);
	pair<int,int> b=mp(x[B],y[B]);
	pair<int,int> c=mp(x[C],y[C]);
	int tmp=a.fr*(b.sc-c.sc)+b.fr*(c.sc-a.sc)+c.fr*(a.sc-b.sc);
	if(tmp<0) return 0;
	if(tmp>0) return 1;
	return 2;
}
void solve(){
	int n,h;cin>>n>>h;
	for(int i=0;i<n;i++)
		cin>>x[i]>>y[i];
	vector<double> l(n),r(n);
	vector< pair<double,double> > v;
	deque<int> st;
	st.pb(0);
	for(int i=1;i<n;i++){
		while(st.size()>1 && cross(st[st.size()-2],st.back(),i)!=0)
			st.pop_back();
		if(i%2==0){
			if(slope(i,st.back())==0) l[i]=-INF;
			else l[i]=x[st.back()]+(h-y[st.back()])/slope(i,st.back());
		}
		
		st.push_back(i);
	}
	while(!st.empty()) st.pop_back();
	st.pb(n-1);
	for(int i=n-2;i>=0;i--){
		while(st.size()>1 && cross(st[st.size()-2],st.back(),i)!=1)
			st.pop_back();
		if(i%2==0){
			if(slope(st.back(),i)==0) r[i]=INF;
			else r[i]=x[i]+(h-y[i])/slope(st.back(),i);
		}
		st.push_back(i);
	}
	for(int i=2;i<n-1;i+=2) v.pb(mp(l[i],r[i]));
	sort(all(v));
	int ans=0;
	double rx=-INF;
	for(int i=0;i<v.size();i++){
		if(rx+1e-9>=l[i]){
			continue;
		}
		ans++;
		rx=r[i];
	}
	//cout<<fixed<<setprecision(3);
	/*for(auto it: v)
		cout<<it.fr<<' '<<it.sc<<endl;*/
	cout<<ans;
}
int main(){
	solve();
}

Compilation message (stderr)

Main.cpp: In function 'void solve()':
Main.cpp:64:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<long double, long double> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   64 |  for(int i=0;i<v.size();i++){
      |              ~^~~~~~~~~

• Subtask 1: 0 / 20
• Subtask 2: 0 / 30
• Subtask 3: 0 / 60