Submission #1208715

#	Time	Username	Problem	Language	Result	Execution time	Memory
1208715		catsarecool5530	Mobile (BOI12_mobile)	C++20	4 / 100	1097 ms	47328 KiB

mobile

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define endl "\n";
#define all(x) x.begin(), x.end()
#define int long long
int MOD = 1e9 + 7;
const ll INF = 1e18;


void solve() {
    int n, l; cin >> n >> l;
    vector<array<int, 2>> arr(n);
    for (int i = 0; i < n; i++) {
        cin >> arr[i][0] >> arr[i][1];
    }
    auto works = [&](long double r) {
        vector<array<long double, 2>> cover(n);
        for (int i = 0; i < n; i++) {
            if (arr[i][1] > r) {
                cover[i][0] = -1e18; 
                cover[i][1] = -1e18;
                continue;
            }
            cover[i][0] = arr[i][0] - sqrt(r * r - arr[i][1] * arr[i][1]);
            cover[i][1] = arr[i][0] + sqrt(r * r - arr[i][1] * arr[i][1]);
        }
        sort(all(cover));
        long double cur = 0;
        for (int i = 0; i < n; i++) {
            if (cover[i][0] > cur) continue;
            cur = max(cur, cover[i][1]);
        }
        return cur >= l;
    };
    long double l1 = 0, r = 1e9;
    while (r - l1 > 1e-9) {
        long double mid = (l1 + r) / 2;
        if (works(mid)) {
            r = mid;
        } else {
            l1 = mid;
        }
    }
    cout << fixed << setprecision(10) << r << endl;

}
 
signed main() {
    ios::sync_with_stdio(0); cin.tie(NULL);
    // freopen("walk.in", "r", stdin);
    // freopen("walk.out", "w", stdout);
    ll t = 1; // cin >> t;
    while (t--) {
        solve();
    }
}

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