Submission #738453

#	Time	Username	Problem	Language	Result	Execution time	Memory
738453		LKR__enjoyer	Mobile (BOI12_mobile)	C++17	50 / 100	1085 ms	57672 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)
{
    while(hi-lo>1e-3)
    {
        ld mid=(lo+hi)/2; 
        if(spr(mid))hi=mid; else lo=mid;
    }
    return lo;
}

int main()
{ 
    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;
sort(pts.begin(),pts.end());
if(pts[0].f>0)return 0;    
ld maxi=pts[0].s;
for(int i=1;i<pts.size();i++)
{if(pts[i].f>maxi&&pts[i].f>0)return 0; maxi=max(maxi,pts[i].s); if(pts[i].s>=(ld)l)return 1;}
    if(maxi<ld(l))return 0;
return 1;    
}

Compilation message (stderr)

mobile.cpp: In function 'bool spr(ld)':
mobile.cpp:47:14: 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]
   47 | for(int i=1;i<pts.size();i++)
      |             ~^~~~~~~~~~~

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