# | Time | Username | Problem | Language | Result | Execution time | Memory |
---|---|---|---|---|---|---|---|
1056895 | TimAni | Mobile (BOI12_mobile) | C++17 | 1080 ms | 40672 KiB |
This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
// time-limit: 3000
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const double eps = 1E-4;
struct point {
int x{}, y{};
};
void solve() {
int n, L;
cin >> n >> L;
vector<point> p(n);
for(int i = 0; i < n; i++) {
cin >> p[i].x >> p[i].y;
}
auto intersection = [&](const point& A, double R) -> array<double, 2> {
if(abs(A.y) > R) {
assert(1);
return {L, -1};
}
double D = 1.0 * R * R - 1.0 * A.y * A.y; // divided by 4
double x1 = A.x - sqrt(D);
double x2 = A.x + sqrt(D);
if(x2 < x1) swap(x1, x2);
return {x1, x2};
};
auto good = [&](double R) {
vector<array<double, 2>> segs;
for(int i = 0; i < n; i++) {
if(abs(p[i].y) > R) continue;
segs.push_back(intersection(p[i], R));
}
if(segs.empty()) return false;
sort(segs.begin(), segs.end());
double l = segs[0][0], r = segs[0][1];
int i = 0;
while(i + 1 < segs.size() && segs[i + 1][0] <= r) {
r = max(segs[i + 1][1], r);
i++;
}
return r >= L && l <= 0;
};
double l = 0, r = 4e9;
while(r - l > eps) {
double R = (r + l) / 2;
if(good(R)) {
r = R;
}
else {
l = R;
}
}
cout << fixed << setprecision(-log10(eps)) << r << endl;
}
int main() {
cin.tie(0)->sync_with_stdio(0);
double T = 1;
//cin >> T;
while(T--) solve();
return 0;
}
Compilation message (stderr)
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