Submission #948288

#	Time	Username	Problem	Language	Result	Execution time	Memory
948288		Amaarsaa	Mobile (BOI12_mobile)	C++14	100 / 100	322 ms	35692 KiB

mobile

#include<bits/stdc++.h>

using namespace std;
using ll = long long ;

ll n, l;
ll x[1000005], y[1000005];
bool Can(double R) {
	double D, x1, x2, mx = 0.0;
	for (int j = 1; j <= n; j ++) {
		D = R * R - y[j] * y[j];
		D = sqrt(D);
		x1 = x[j] - D;
		x2 = x[j] + D;
		if ( x1 <= mx) mx = max(mx,x2);
	}
	if ( mx < l) return false;
	return true;
}

int main() {
	ios::sync_with_stdio(false);
	cin.tie(NULL);
	ll i;
	double lo , hi, mid;
	cin >> n >> l;
	
	for (i = 1; i <= n; i ++) {
		cin >> x[i] >> y[i];
	}
	lo = 0;
	hi = 1.5e9;
	
	while (hi - lo > 1e-3) {
 		mid = (lo + hi)/2;
		if (!Can(mid)) lo = mid;
		else hi = mid;
	}	
	cout << fixed << setprecision(4) << lo << "\n";
}

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