Submission #493543

#	Time	Username	Problem	Language	Result	Execution time	Memory
493543		imaginary_unit	Mobile (BOI12_mobile)	C++17	100 / 100	417 ms	17228 KiB

mobile

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

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

bool ok(double r)
{
    double cur=0;
    for(int i=0; i<n; i++){
        double delta=sqrt(r*r-y[i]*y[i]), a=x[i]-delta, b=x[i]+delta;
        if(a<=cur){
            cur=max(cur, b);
        }
    }
    return cur >= len;
}

double MinRadius(double l, double r)
{
    while(r-l>1e-4){
        double m=(l+r)/2;
        if(ok(m)){
            r=m;
        }
        else{
            l=m;
        }
    }
    return r;
}

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

    cin >> n >> len;
    for(int i=0; i<n; i++){
        cin >> x[i] >> y[i];
    }
    cout << fixed << setprecision(4) << MinRadius(0, 1.5e9);
    return 0;
}

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