Submission #1216139

#	Time	Username	Problem	Language	Result	Execution time	Memory
1216139		Ghulam_Junaid	Event Hopping (BOI22_events)	C++20	20 / 100	86 ms	15280 KiB

events

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

const int N = 1e5 + 10, LG = 18;
int n, q, par[N][LG], a[N][2];
vector<pair<pair<int, int>, int>> vec;

int main(){
    ios::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    memset(par, -1, sizeof par);

    cin >> n >> q;
    for (int i = 0; i < n; i ++){
        int s, e;
        cin >> s >> e;
        a[i][0] = s, a[i][1] = e;
        vec.push_back({{s, 0}, i});
        vec.push_back({{e, 1}, i});
    }
    sort(vec.begin(), vec.end());

    set<pair<int, int>> st;
    for (auto P : vec){
        auto [E, i] = P;
        if (!E.second)
            st.insert({a[i][1], i});
        else{
            st.erase({a[i][1], i});
            if (st.empty())
                par[i][0] = -1;
            else{
                auto R = *st.rbegin();
                par[i][0] = R.second;
            }
        }
    }

    for (int j = 1; j < LG; j ++)
        for (int i = 0; i < n; i ++)
            if (par[i][j - 1] != -1)
                par[i][j] = par[par[i][j - 1]][j - 1];

    for (int i = 0; i < q; i ++){
        int l, r;
        cin >> l >> r;
        l--, r--;

        if (a[r][1] < a[l][1]){
            cout << "impossible\n";
            continue;
        }

        if (a[r][1] == a[l][1]){
            cout << 1 - (l == r) << '\n';
            continue;
        }

        int cur = l, ans = 0;
        for (int j = LG - 1; j >= 0; j --){
            if (par[cur][j] == -1) continue;
            if (a[par[cur][j]][1] < a[r][1])
                cur = par[cur][j], ans += (1 << j);
        }

        if (par[cur][0] == -1){
            cout << "impossible\n";
            continue;
        }

        cout << ans + 1 << '\n';
    }
}

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