Submission #868538

#	Time	Username	Problem	Language	Result	Execution time	Memory
868538		Dec0Dedd	Event Hopping (BOI22_events)	C++14	30 / 100	93 ms	33992 KiB

events

#include <bits/stdc++.h>

using namespace std;

typedef pair<int, int> pii;

const int N = 1e5+10;
const int K = 20;
const int INF = 1e6+10;

int up[K][N], d[K][N], s[N], lf[N], e[N], mx[N], idx[N], n, q;
vector<pii> v;
vector<int> add[N], rm[N];

bool cmp(pii a, pii b) {
    if (a.first == b.first) return s[a.second] < s[b.second];
    else return a.first < b.first;
}

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(NULL);

    cin>>n>>q;
    for (int i=0; i<n; ++i) {
        cin>>s[i]>>e[i];
        v.push_back({e[i], i});
    } sort(v.begin(), v.end(), cmp);

    for (int i=0; i<n; ++i) {
        int j=lower_bound(v.begin(), v.end(), make_pair(s[v[i].second], -1))-v.begin();
        lf[i]=j;
        add[lf[i]].push_back(v[i].second);
        rm[i+1].push_back(v[i].second);
    }

    for (int i=0; i<n; ++i) idx[v[i].second]=i;

    multiset<pii> ms;
    for (int i=0; i<n; ++i) {
        for (auto u : add[i]) ms.insert({e[u], idx[u]});
        for (auto u : rm[i]) ms.erase(ms.find({e[u], idx[u]}));
        mx[i]=ms.rbegin()->second;
    }

    for (int i=n-1; i>=0; --i) {
        up[0][i]=mx[i], d[0][i]=(mx[i] != i);
        for (int j=1; j<K; ++j) {
            up[j][i]=up[j-1][up[j-1][i]];
            d[j][i]=d[j-1][i]+d[j-1][up[j-1][i]];
        }
    }

    /*
    cout<<"v: ";
    for (int i=0; i<n; ++i) cout<<v[i].first<<" ";
    cout<<"\n";

    cout<<"idx: ";
    for (int i=0; i<n; ++i) cout<<idx[i]<<" ";
    cout<<"\n";

    cout<<"mx: ";
    for (int i=0; i<n; ++i) cout<<mx[i]<<" ";
    cout<<"\n";
    */

    while (q--) {
        int l, r; cin>>l>>r; --l, --r;
        l=idx[l], r=idx[r];

        //cout<<"QUE "<<l<<", "<<r<<"\n";

        if (l == r) {
            cout<<0<<"\n";
            continue;
        }

        if (v[r].first < v[l].first) {
            cout<<"impossible\n";
            continue;
        }

        int ans=0;
        for (int j=K-1; j>=0; --j) {
            //cout<<"HERE "<<up[j][l]<<"\n";
            if (up[j][l] <= r) ans+=d[j][l], l=up[j][l];
        }

        if (l == r) ans+=0;
        else {
            if (s[v[r].second] <= e[v[l].second] && e[v[l].second] <= e[v[r].second]) ++ans, l=r;
            else {
                cout<<"impossible\n";
                continue;
            }
        }

        assert(l == r);
        cout<<ans<<"\n";
    }
}

• Subtask 1: 10 / 10
• Subtask 2: 0 / 10
• Subtask 3: 0 / 15
• Subtask 4: 0 / 15
• Subtask 5: 20 / 20
• Subtask 6: 0 / 30