Submission #1056881

#	Time	Username	Problem	Language	Result	Execution time	Memory
1056881		TimAni	Mobile (BOI12_mobile)	C++17	60 / 100	470 ms	8256 KiB

mobile

#include <bits/stdc++.h>
#define long long long
 
using namespace std;
 
const double eps = 1E-3;
const int N = (int) 1E6;
 
int n, k;
int x[N], y[N];
 
bool valid(double a) {
	double t = 0;
	for (int i = 0; i < n; i++) {
		if (a < y[i]) {
			continue;
		} 
		double l = x[i] - sqrt(1.0 * a * a - 1.0 * y[i] * y[i]);
		double r = x[i] + sqrt(1.0 * a * a - 1.0 * y[i] * y[i]);
		if (l <= t && r >= t) {
			t = r;
		}
	}
	return t >= k;
}
 
void solve() {
	cin >> n >> k;
	for (int i = 0; i < n; i++) {
		cin >> x[i] >> y[i];
	}
	
    double l = 0, r = 4E9;
    while(r - l > eps) {
        double R = (r + l) / 2;
        if(valid(R)) {
            r = R;
        }
        else {
            l = R;
        }
        
    }
    cout << fixed << setprecision(-log10(eps)) << r << endl;
}
 
int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int t;
	t = 1;
	for (int i = 0; i < t; i++) {
		solve();
	}
	return 0;
}

// time-limit: 3000

• Subtask 1: 4 / 4
• Subtask 2: 4 / 4
• Subtask 3: 4 / 4
• Subtask 4: 4 / 4
• Subtask 5: 4 / 4
• Subtask 6: 5 / 5
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• Subtask 15: 5 / 5
• Subtask 16: 5 / 5
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• Subtask 18: 0 / 5
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• Subtask 20: 5 / 5
• Subtask 21: 5 / 5