Submission #578080

#	Time	Username	Problem	Language	Result	Execution time	Memory
578080		balbit	Event Hopping (BOI22_events)	C++14	100 / 100	237 ms	30028 KiB

events

#include <bits/stdc++.h>
using namespace std;

#define ll long long
#define pii pair<ll, ll>
#define f first
#define s second

#define SZ(x) (int)((x).size())
#define ALL(x) (x).begin(), (x).end()
#define pb push_back

#define FOR(i,a,b) for (int i = a; i<b; ++i)
#define REP(i,n)  FOR(i,0,n)
#define REP1(i,n) FOR(i,1,n+1)

#define MX(a,b) a = max(a,b)
#define MN(a,b) a = min(a,b)
#ifdef BALBIT
#define bug(...) cerr<<"#"<<__LINE__<<": "<<#__VA_ARGS__<<"- ", _do(__VA_ARGS__)
template<typename T> void _do( T && x) {cerr<<x<<endl;}
template<typename T,typename ...S> void _do( T && x, S && ...y) {cerr<<x<<", "; _do(y...);}
#else
#define bug(...)
#define endl '\n'
#endif // BALBIT

const int maxn = 2e5+5;
vector<pii> to[maxn]; // {lpos,id}

vector<pii> ask[maxn]; // for each seg id, the left pos and the queryid
int ans[maxn];
int fa[18][maxn];
struct seg{
    int l,r,i;
    bool operator < (seg o) {
        return r < o.r;
    }
};

signed main(){
    ios::sync_with_stdio(0), cin.tie(0);

    bug(1,2);

    int n,q; cin>>n>>q;
    vector<pii>v(n);
    vector<ll>xpos;
    REP(i,n) {
        cin>>v[i].f>>v[i].s;
        xpos.pb(v[i].f);
        xpos.pb(v[i].s);
    }
    sort(ALL(xpos)); xpos.resize(unique(ALL(xpos)) - xpos.begin());

    auto getx = [&](ll x) {return lower_bound(ALL(xpos), x)-xpos.begin();};

    REP(i,n) {
        v[i].f = getx(v[i].f);
        v[i].s = getx(v[i].s);
        to[v[i].s].pb({v[i].f,i});
    }

    REP(i,q) {
        int s,e; cin>>s>>e; --s; --e;
        if (s == e) {
            ans[i] = 0; continue;
        }
        ask[e].pb({v[s].s,i});
    }

    vector<seg> now;


    REP(r, maxn)  {
        sort(ALL(to[r]));
        for (pii T : to[r]) {
            int l= T.f, i =T.s;
            while (SZ(now)  && l <= now[SZ(now)-1].l) now.pop_back();

            if (SZ(now) && now.back().r >= l) {
                fa[0][i] = lower_bound(ALL(now), seg{l,l,i})->i;
            }else{
                fa[0][i] = i;
            }
            for (int j = 1; j<18; ++j) {
                fa[j][i] = fa[j-1][fa[j-1][i]];
            }
            now.pb({l,r,i});

            for (pii qq : ask[i]) {
                if (qq.f > r) {
                    ans[qq.s] = -1; continue;
                }
                int steps =0;
                int at = i;
                for (int j = 17; j>=0; --j) {
                    if (v[fa[j][at]].f > qq.f) {
                        steps += (1<<j);
                        at = fa[j][at];
                    }
                }
                if (v[at].f > qq.f) {
                    at = fa[0][at]; ++steps;
                }
                if (v[at].f > qq.f) {
                    ans[qq.s] = -1;
                }else{
                    ans[qq.s] = steps+1;
                }
            }
        }
    }
    REP(i,q) {
        if (ans[i] == -1) cout<<"impossible"<<endl;
        else cout<<ans[i]<<endl;
    }
}

• Subtask 1: 10 / 10
• Subtask 2: 10 / 10
• Subtask 3: 15 / 15
• Subtask 4: 15 / 15
• Subtask 5: 20 / 20
• Subtask 6: 30 / 30