Submission #781096

#	Time	Username	Problem	Language	Result	Execution time	Memory
781096		uped	Mobile (BOI12_mobile)	C++14	100 / 100	378 ms	15956 KiB

mobile

// ~uped
#include<bits/stdc++.h>

using namespace std;

using ll = long long;

void fastio() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
}

int main() {
    fastio();
    int n, len;
    cin >> n >> len;
    vector<pair<ll, ll>> v(n);
    for (int i = 0; i < n; ++i) {
        int a, b;
        cin >> a >> b;
        v[i] = {a, b};
    }
    // binary search radius
    double l = 0.0, r = 1e10;
    while (r - l > 1e-3) {
        double radius = (l + r) / 2.0;
        double mx = 0;
        for (int j = 0; j < n; ++j) {
            ll x = v[j].first;
            ll y = v[j].second;
            // a*a+b*b=c*c => c*c-b*b=a*a
            double a = sqrt( radius * radius - y * y);
            // we cover segment from x - a to x + a
            if (x - a <= mx) {
                mx = max(x + a, mx);
            }
        }
        if (mx >= len) {
            r = radius;
        } else {
            l = radius;
        }
    }
    cout <<  setprecision(20) << r;
    return 0;
}

• Subtask 1: 4 / 4
• Subtask 2: 4 / 4
• Subtask 3: 4 / 4
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• Subtask 20: 5 / 5
• Subtask 21: 5 / 5