Submission #493540

#	Time	Username	Problem	Language	Result	Execution time	Memory
493540		imaginary_unit	Mobile (BOI12_mobile)	C++17	100 / 100	448 ms	16232 KiB

mobile

#include<bits/stdc++.h>
#define ll long long
#define fi first
#define se second
using namespace std;

ll x[1'000'000], y[1'000'000];

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);

    int n, len;
    cin >> n >> len;
    for(int i=0; i<n; i++){
        cin >> x[i] >> y[i];
    }

    double l=1, r=1.5e9;
    while(r-l>1e-3){
        double m=(l+r)/2, cur=0;
        for(int i=0; i<n; i++){
            double delta=sqrt(m*m-y[i]*y[i]);
            double a=x[i]-delta, b=x[i]+delta;
            if(a<=cur){
                cur=max(cur, b);
            }
        }
        if(cur>=len){
            r=m;
        }
        else{
            l=m;
        }
    }
    cout << fixed << setprecision(4) << l;
    return 0;
}

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