Submission #576646

#	Time	Username	Problem	Language	Result	Execution time	Memory
576646		InternetPerson10	Event Hopping (BOI22_events)	C++17	10 / 100	1600 ms	43756 KiB

events

#include <bits/stdc++.h>
typedef long long ll;

using namespace std;

set<int> s;
map<int, int> idx;
map<pair<int, int>, int> toEvent;
vector<pair<int, int>> p;
vector<int> mini;

struct SegTree {
    int lx, rx;
    int val = 1e9, id = -1;
    SegTree *ls, *rs;
    SegTree(int l, int r) {
        lx = l;
        rx = r;
        if(rx - lx > 1) {
            int mid = (lx + rx) / 2;
            ls = new SegTree(lx, mid);
            rs = new SegTree(mid, rx);
            val = min(ls->val, rs->val);
            if(val == ls->val) id = ls->id;
            if(val == rs->val) id = rs->id;
        }
        else {
            val = mini[lx];
            id = lx;
        }
    }
    pair<int, int> getMin(int l, int r) {
        if(l <= lx && rx <= r) return {val, id};
        if(r <= lx || rx <= l) return {1e9, -1};
        return min(ls->getMin(l, r), rs->getMin(l, r));
    }
};

vector<int> v;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n, q;
    cin >> n >> q;
    int g = 1;
    while(g <= 2*n) g *= 2;
    p.resize(n);
    mini.resize(g, 1e9);
    for(int i = 0; i < n; i++) {
        cin >> p[i].first >> p[i].second;
        s.insert(p[i].first);
        s.insert(p[i].second);
    }
    for(int y : s) {
        idx[y] = idx.size();
    }
    for(int i = 0; i < n; i++) {
        p[i].first = idx[p[i].first];
        p[i].second = idx[p[i].second];
        int x, y;
        tie(x, y) = p[i];
        mini[y] = min(mini[y], x);
        toEvent[p[i]] = i;
    }
    SegTree st(0, g);
    while(q--) {
        int x, y;
        cin >> x >> y;
        x--; y--;
        if(x == y) {
            cout << "0\n";
            continue;
        }
        int ans = 1;
        while(p[x] != p[y]) {
            if(p[y].first <= p[x].second && p[x].second <= p[y].second) {
                break;
            }
            pair<int, int> pa = st.getMin(p[y].first, p[y].second + 1);
            if(pa.second == -1 || pa == p[y]) {
                ans = -1;
                break;
            }
            ans++;
            y = toEvent[pa];
        }
        if(ans == -1) {
            cout << "impossible\n";
            continue;
        }
        else {
            cout << ans << '\n';
        }
    }
}

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