Submission #738461

#	Time	Username	Problem	Language	Result	Execution time	Memory
738461		LKR__enjoyer	Mobile (BOI12_mobile)	C++17	50 / 100	1082 ms	57668 KiB

mobile

#include <iostream>
#include<bits/stdc++.h>
#define pb push_back
#define f first
#define s second
typedef long long ll;
typedef long double ld;
using namespace std;
int n,l;
vector<pair<int,int>> pkt;
bool spr(long double rad);
long double bin(ld lo,ld hi)
{
    for(int i=0;i<40;i++)
    {
        ld mid=(lo+hi)/2; 
        if(spr(mid))hi=mid; else lo=mid;
    }
    return lo;
}

int main()
{  ios_base::sync_with_stdio();
 cin.tie();
    cin>>n>>l;
    for(int i=0;i<n;i++)
    {int a,b; cin>>a>>b;
    pkt.pb({a,b});    
    }
    cout<<fixed<<setprecision(4)<<bin(0,(ld)(2*l));
    
    return 0;
}
bool spr(ld rad){
vector<pair<ld,ld>> pts={};
for(auto p : pkt)
{
    ld x=(ld)p.f,y=(ld)p.s;
    if(rad<abs(y))continue; 
    ld del=(ld)sqrt(rad*rad-y*y);
    ld x1=x-del,x2=x+del; 
    pts.pb({x1,x2});
}
if(pts.empty())return 0;
ld curr_min=1.5e9+1,curr_max=-1.5e9-1;
for(auto i : pts)
{ ld a=i.f,b=i.s; if(b<0)continue; 
if(curr_min==1.5e9+1&&curr_max==-1.5e9-1){curr_min=a; curr_max=b; continue;}
if(a<=curr_max)curr_max=max(curr_max,b);
if(b>=curr_min)curr_min=min(curr_min,a);
}
if(curr_min>0||curr_max<(ld)l)return 0;
return 1;    
}

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