Submission #1010128

#TimeUsernameProblemLanguageResultExecution timeMemory
1010128Psiuk_YuriiMobile (BOI12_mobile)C++14
100 / 100
474 ms50852 KiB
#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef long double ld;
typedef pair<ll,ll> pll;
typedef pair<ld,ld> pld;
typedef pair<ll,pll> ppl;

ll n;
ld u,L,R,eps;
pld p[1000009];

bool can(ld R){
   ld r=0.0;
   for(int i=1;i<=n;i++){
       if(R>=p[i].second){
           ld x0=p[i].first-sqrt(R*R-p[i].second*p[i].second);
           if(x0<=r) {
                ld x1=p[i].first+sqrt(R*R-p[i].second*p[i].second);
                r=max(x1,r);
                if(r>=u) return true;
           }
       }
   }
  return false;
}
int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    cin>>n>>u;
    for(int i=1;i<=n;i++) {cin>>p[i].first>>p[i].second; p[i].second=abs(p[i].second);}
    eps=0.001;
    L=0.0; R=1000000000.0;
    while(L<R-eps){
        ld mid=(L+R)*0.5;
        if(can(mid)) R=mid;
        else L=mid;
    }
    cout<<fixed<<setprecision(5)<<L;


    return 0;
}
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