Submission #1124540

#	Time	Username	Problem	Language	Result	Execution time	Memory
1124540		DON_F	Mobile (BOI12_mobile)	C++20	0 / 100	679 ms	41152 KiB

mobile

#include<bits/stdc++.h>
using namespace std;
using ll = long long;
#define all(x) x.begin(), x.end()
#define L(i, b, e) for (int i = b; i < e; ++i)
#define R(i, b, e) for (int i = b; i >= e; --i)
#define pb emplace_back
#define vi vector<int>
#define sz(x) ((int) x.size())
const int N = 1e6 + 7, Mx = 1e9 + 9;
int n, l;
int x[N], y[N];
using ld = long double;
ld dis(pair<ld, int> p1, pair<int, int> p2){
    return (ld) abs(p1.first - p2.first) * abs(p1.first - p2.first) + (ld) abs(p1.second - p2.second) * abs(p1.second - p2.second);
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cin >> n >> l;
    L(i, 0, n){
        cin >> x[i] >> y[i];
    }
    vector<pair<ld, int>> st;
    st.pb(0, 0);
    const ld E = 1e-4;
    L(i, 1, n){
        ld ed = l + 1;
        while (!st.empty()){
            ld lo = 0, hi = l, res = -1;
            ld fs = st.back().first;
            int id = st.back().second;
            while (lo <= hi){
                ld mid = lo + (hi - lo) / 2;
                if (dis({mid, 0}, {x[i], y[i]}) < dis({mid, 0}, {x[id], y[id]})){
                    res = mid;
                    hi = mid - E;
                }else{
                    lo = mid + E;
                }
            }
            if (res != -1){
                ed = res;
                if (res <= fs){
                    st.pop_back();
                }else{
                    break;
                }
            }else{
                break;
            }
        }
        if (ed != l + 1){
            st.pb(ed, i);
        }
    }
    st.pb(l + E, l + 1);
    ld ans = 0;
    L(i, 0, sz(st) - 1){
        ans = max(ans, dis({st[i].first, 0}, {x[st[i].second], y[st[i].second]}));
        ans = max(ans, dis({st[i + 1].first - E, 0}, {x[st[i].second], y[st[i].second]}));
    }
    long double f = sqrtl(ans);
    cout << fixed << setprecision(6) << f;
}

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