Submission #639218

#	Time	Username	Problem	Language	Result	Execution time	Memory
639218		Pietra	Mobile (BOI12_mobile)	C++14	100 / 100	830 ms	16212 KiB

mobile

#include<bits/stdc++.h>
using namespace std ;

const int maxn = 2e6 + 5 ;
const double inf = 2e9 + 5 ;

double n, l, x[maxn], y[maxn] ;

bool check(double r){

    double f = 0 ;

    for(int i = 1 ; i <= n ; i++){
        if(r < y[i]) continue ;
        double dx = sqrt(((r*r) - (y[i]*y[i]))) ;
        double ini = x[i] - dx, fim = x[i] + dx ;
        if(ini <= f) f = max(f, fim) ;
    }

    return (f >= l) ;
}

int main(){

    ios_base::sync_with_stdio(false) ; cin.tie(NULL) ;

    cin >> n >> l ;

    for(int i = 1 ; i <= n ; i++) cin >> x[i] >> y[i] ;

    double ini = 0, fim = inf, mid ;

    int it = 41 ;
    while(it--){
        mid = (ini + fim)/2 ;
        if(check(mid)) fim = mid ;
        else ini = mid ;
    }

    cout << fixed << setprecision(4) << fim << "\n" ;

}

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