Submission #1093825

#	Time	Username	Problem	Language	Result	Execution time	Memory
1093825		damamila	Mobile (BOI12_mobile)	C++17	0 / 100	213 ms	32464 KiB

mobile

#include <bits/stdc++.h>

using namespace std;

#define int long long

int n, l;
vector<pair<int, int>> points;

pair<double, double> circle_intersection(int i, double r) {
	auto [x, y] = points[i];
	double tmp = sqrt(r*r-y*y);
	double x1 = x-tmp;
	double x2 = x+tmp;
	if (x2 < x1) swap(x1, x2);
	return {x1, x2};
}

void solve() {
	double ub = 10, lb = 0; //change later
	double m;
	while (lb+0.0001 < ub) {
		//~ cout << m << endl;
		m = (lb+ub)/2;
		double reach = 0;
		bool ja = 1;
		for (int i = 0; i < n; i++) {
			auto [x1, x2] = circle_intersection(i, m);
			if (reach+0.0001 < x1) ja = 0;
			reach = max(reach, x2);
		}
		if (reach+0.0001 < l) ja = 0;
		if (ja) {
			ub = m;
		} else {
			lb = m+0.0001;
		}
		//~ cout << ja << " " << lb << " " << ub << " " << endl;
	}
	cout << ub << endl;
}

signed main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);  
	cin >> n >> l;
	cout << fixed << setprecision(4);
	points = vector<pair<int, int>> (n);
	for (int i = 0; i < n; i++) {
		cin >> points[i].first >> points[i].second;
	}
	solve();
}

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