제출 #1249032

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
1249032		PokemonMaster	Mobile (BOI12_mobile)	C++20	4 / 100	574 ms	20184 KiB

mobile

#include<bits/stdc++.h>
using namespace std;
double dist(double x1,double y1,double x2,double y2)
{
    return sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
}
double eq(double x1,double y1,double x2,double y2)
{
    return (x1*x1+y1*y1-x2*x2-y2*y2)/(2.0*(x1-x2));
}
signed main()
{
    int n,l;
    cin>>n>>l;
    vector <double> x(n+1);
    vector <double> y(n+1);
    for(int i=1;i<=n;i++)cin>>x[i]>>y[i];
    for(int i=1;i<=n;i++)y[i]=abs(y[i]);
    deque <int> stk;
    for(int i=1;i<=n;i++)
    {
        if(stk.size() && x[i]==x[stk.back()])
        {
            if(y[i]>=y[stk.back()])continue;
            stk.pop_back();
        }
        while(stk.size()>1 && eq(x[i],y[i],x[stk.back()],y[stk.back()])<eq(x[stk.back()],y[stk.back()],x[stk[stk.size()-2]],y[stk[stk.size()-2]]))stk.pop_back();
        stk.push_back(i);
    }
    while(stk.size()>1 && eq(x[stk[0]],y[stk[0]],x[stk[1]],y[stk[1]])<0)stk.pop_front();
    while(stk.size()>1 && eq(x[stk[stk.back()]],y[stk[stk.back()]],x[stk[stk.size()-2]],y[stk[stk.size()-2]])>l)stk.pop_back();
    double mx=0;
    for(int i=0;i<stk.size();i++)
    {
        if(i)
        {
            double inr=eq(x[stk[i]],y[stk[i]],x[stk[i-1]],y[stk[i-1]]);
            if(inr<0 || inr>l)continue;
            mx=max(mx,dist(inr,0,x[stk[i]],y[stk[i]]));
        }else
        {
            mx=max(mx,dist(0,0,x[stk[i]],y[stk[i]]));
        }
         if(i<stk.size()-1)
        {
            double inr=eq(x[stk[i]],y[stk[i]],x[stk[i+1]],y[stk[i+1]]);
            if(inr<0 || inr>l)continue;
            mx=max(mx,dist(inr,0,x[stk[i]],y[stk[i]]));
        }else
        {
            mx=max(mx,dist(l,0,x[stk[i]],y[stk[i]]));
        }
    }
    cout<<fixed<<setprecision(6)<<mx;
}

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