Submission #1130329

#	Time	Username	Problem	Language	Result	Execution time	Memory
1130329		liangjeremy	Mobile (BOI12_mobile)	C++20	0 / 100	1096 ms	31812 KiB

mobile

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double lb;

int n,l;
vector<pair<lb,lb>>a;

bool check(lb radius){
    lb start=0;
    for(int i=0; i<n; i++){
        lb left=a[i].first-sqrt(radius*radius-a[i].second*a[i].second);
        lb right=sqrt(radius*radius-a[i].second*a[i].second)+a[i].first;
        if(left>start)return false;
        start=max(start,right);
    }
    if(start<l)return false;
    return true;
}

 
int main(){
    ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    cin>>n>>l; a.resize(n);
    for(int i=0; i<n; i++){
        cin>>a[i].first>>a[i].second;
    }
    lb left=0; lb right=2*(1e9); lb prec=1e-5;
    while(right-left>prec){
        lb mid=(left+right)/2;
        if(check(mid))right=mid;
        else left=mid+prec;
    }
    cout<<fixed<<setprecision(5)<<left<<'\n';
}

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