Submission #950208

#	Time	Username	Problem	Language	Result	Execution time	Memory
950208		Baytoro	Planine (COCI21_planine)	C++17	0 / 110	76 ms	4152 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
const ll INF=1e18,N=2e5+5;
bool cmp(pair<double,double> a, pair<double,double> b){
	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(pair<int,int> a, pair<int,int> b){
	return a.fr*b.sc-a.sc*b.fr;
}
int cross(int a, int b, int c){
	return cross(mp(x[b]-x[a],y[b]-y[a]),mp(x[c]-x[a],y[c]-y[a]));
}
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;
			/*cout<<i<<':';
			for(auto it: st)
				cout<<' '<<it;
			cout<<endl;*/
			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)<0)
			st.pop_back();
		if(i%2==0){
			//if(slope(st.back(),i)==0) r[i]=INF;
			r[i]=x[i]+(h-y[i])/slope(st.back(),i);
		}
		st.push_back(i);
	}
	/*for(int i=2;i<n-1;i+=2){
		double slope=(y[i+1]-y[i])/(x[i+1]-x[i]+0.0);
		//r[i]=x[i]+(h-y[i])/slope;
		slope = (y[i]-y[i-1])/(x[i]-x[i-1]+0.0);
		r[i]=x[i-1]+(h-y[i-1])/slope;
		//v.pb(mp(l[i],r[i]));
	}*/
	//cout<<fixed<<setprecision(3);
	for(int i=2;i<n-1;i+=2) v.pb(mp(l[i],r[i]));
	sort(all(v), cmp);
	/*for(int i=0;i<n;i++)
		cout<<l[i]<<' '<<r[i]<<endl;*/
	int ans=1;
	double rx=v[0].sc;
	for(int i=1;i<v.size();i++){
		if(v[i].fr>rx+1e-9){
			rx=v[i].sc;
			ans++;
		}
	}
	//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:72:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<double, double> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   72 |  for(int i=1;i<v.size();i++){
      |              ~^~~~~~~~~

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