Submission #973226

#	Time	Username	Problem	Language	Result	Execution time	Memory
973226		HuyAT	Mobile (BOI12_mobile)	C++14	100 / 100	731 ms	16208 KiB

mobile

#include<bits/stdc++.h>

const int MaxN = 1e6 + 10;
const double Eps = 1e-4;
const double MaxV = 1e9;

int n;
double length,x[MaxN + 1],y[MaxN + 1];

void readData(){
    std::cin >> n >> length;
    for(int i = 1;i <= n;++i){
        std::cin >> x[i] >> y[i];
    }
}
bool f(double mid){
    double l = 0,r = 0;
    for(int i = 1;i <= n;++i){
        if(mid < y[i]){
            continue;
        }
        double distance = sqrt(mid * mid - y[i] * y[i]);
        if(x[i] - distance <= r && x[i] + distance >= l){
            l = std::min(l,x[i] - distance);
            r = std::max(r,x[i] + distance);
        }
    }
    return (l <= 0 && r >= length);
}
double solve(double lo,double hi){
    while(hi - lo > Eps){
        double mid = (lo + hi) / 2;
        if(f(mid)){
            hi = mid;
        }else{
            lo = mid;
        }
//        std::cerr << mid << "\n";
    }
    return hi;
}
int main(){
    std::ios_base::sync_with_stdio(false);
    std::cin.tie(nullptr);std::cout.tie(nullptr);
    readData();
    std::cout << std::fixed << std::setprecision(8) << solve(0,MaxV * 2);
    return 0;
}

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