제출 #284584

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
284584		Benq	Mobile (BOI12_mobile)	C++14	100 / 100	301 ms	32504 KiB

mobile

#include <bits/stdc++.h>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>
 
using namespace std;
using namespace __gnu_pbds;
 
typedef long long ll;
typedef long double ld;
typedef complex<ld> cd;
 
typedef pair<int, int> pi;
typedef pair<ll,ll> pl;
typedef pair<ld,ld> pd;
 
typedef vector<int> vi;
typedef vector<ld> vd;
typedef vector<ll> vl;
typedef vector<pi> vpi;
typedef vector<pl> vpl;
typedef vector<cd> vcd;
 
template <class T> using Tree = tree<T, null_type, less<T>, rb_tree_tag,tree_order_statistics_node_update>;
 
#define FOR(i, a, b) for (int i=a; i<(b); i++)
#define F0R(i, a) for (int i=0; i<(a); i++)
#define FORd(i,a,b) for (int i = (b)-1; i >= a; i--)
#define F0Rd(i,a) for (int i = (a)-1; i >= 0; i--)
 
#define sz(x) (int)(x).size()
#define mp make_pair
#define pb push_back
#define f first
#define s second
#define lb lower_bound
#define ub upper_bound
#define all(x) x.begin(), x.end()
 
const int MOD = 1000000007;
const ll INF = 1e18;
const int MX = 1000001;
 
int N,L;
pi v[MX];
ld tmp[MX];
 
ld perp(pd x, pd y) {
    return (y.f*y.f+y.s*y.s-x.f*x.f-x.s*x.s)/(2*y.f-2*x.f);
}
 
ld dist(pd a, pd b) {
    return sqrt(pow(a.f-b.f,2)+pow(a.s-b.s,2));
}
 
int main() {
    ios_base::sync_with_stdio(0); cin.tie(0);
    cin >> N >> L;
    int nex = 0;
    F0R(i,N) {
        int x,y; cin >> x >> y; y = abs(y);
        if (nex && v[nex-1].f == x) {
            if (y >= v[nex-1].s) continue;
            else nex --;
        }
        while (nex && tmp[nex-1] >= perp(v[nex-1],{x,y})) nex --;
        v[nex] = {x,y};
        if (nex) tmp[nex] = perp(v[nex-1],v[nex]);
        nex ++;
    }
    ld ans = 0;
    F0R(i,nex) {
        ld mn = (i == 0 ? -INF : tmp[i]);
        ld mx = (i == nex-1 ? INF : tmp[i+1]);
        if (mx < 0 || mn > L) continue;
        mn = max(mn,(ld)0), mx = min(mx,(ld)L);
        ans = max(ans,dist(v[i],{mn,0}));
        ans = max(ans,dist(v[i],{mx,0}));
    }
    cout << fixed << setprecision(6) << ans;
}
 
/* Look for:
* the exact constraints (multiple sets are too slow for n=10^6 :( ) 
* special cases (n=1?)
* overflow (ll vs int?)
* array bounds
*/

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