제출 #1271580

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
1271580		VMaksimoski008	Mobile (BOI12_mobile)	C++17	90 / 100	1025 ms	48180 KiB

mobile

#include <bits/stdc++.h>

#define sz(x) (int)x.size()
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define int long long

using namespace std;

using ll = long long;
using ull = unsigned long long;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using pdd = pair<double, double>;

const int mod = 1e9 + 7;
const int LOG = 20;
const int maxn = 1e5 + 5;
const double eps = 1e-9;

int32_t main() {
    ios_base::sync_with_stdio(false);
    cout.tie(0); cin.tie(0);

    int n, L;
    cin >> n >> L;

    vector<int> x(n), y(n);
    for(int i=0; i<n; i++) cin >> x[i] >> y[i];

    double l=1, r=2e9, ans=r;
    for(int it=0; it<50; it++) {
        double mid = (l + r) / 2.0;
        vector<pdd> seg;

        for(int i=0; i<n; i++) {
            if(abs(y[i]) >= mid) continue;
            double len = sqrt(mid * mid - y[i] * y[i]);
            double left = x[i] - len, right = x[i] + len;
            if( right >= 0 && left <= L ) seg.push_back({ max((double)0, x[i] - len), min((double)L, x[i] + len) });
        }

        if(seg.size() == 0) {
            l = mid;
            continue;
        }

        //sort(seg.begin(), seg.end());
        bool ok = 1;
        double mn = 1e9;
        for(auto &s : seg) mn = min(mn, s.first);
        if(mn > 0) ok = 0;

        double lp=seg[0].first, rp=seg[0].second;

        for(int i=1; i<seg.size(); i++) {
            if(seg[i].first <= rp) rp = max(rp, seg[i].second);
        }

        if(ok && rp >= L) ans = min(ans, mid), r = mid;
        else l = mid;
    }

    cout << setprecision(8) << fixed << ans << '\n';
    return 0;
}

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