Submission #1216211

#	Time	Username	Problem	Language	Result	Execution time	Memory
1216211		Ghulam_Junaid	Event Hopping (BOI22_events)	C++20	10 / 100	1597 ms	45816 KiB

events

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

#pragma GCC optimize("O2")
#pragma GCC optimize("Ofast")
#pragma GCC target("avx,avx2,fma")

const int N = 1e5 + 10, LG = 18;
int n, que, par[N][LG], a[N][2], dist[5005][5005];
vector<pair<pair<int, int>, int>> vec;
vector<int> g[N];

int main(){
    ios::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);

    cin >> n >> que;
    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());

    for (int i = 0; i < n; i ++){
        for (int j = 0; j < n; j ++){
            if (i == j) continue;
            if (a[i][0] <= a[j][1] and a[j][1] <= a[i][1])
                g[j].push_back(i);
        }
    }

    queue<int> q;
    for (int s = 0; s < n; s ++){
        for (int j = 0; j < n; j ++)
            dist[s][j] = 1e9;
        dist[s][s] = 0;

        q.push(s);
        while (!q.empty()){
            int v = q.front();
            q.pop();

            for (int u : g[v]){
                if (dist[s][u] > dist[s][v] + 1){
                    dist[s][u] = dist[s][v] + 1;
                    q.push(u);
                }
            }
        }
    }

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

        if (dist[l][r] > 1e8)
            cout << "impossible\n";
        else
            cout << dist[l][r] << '\n';
        continue;

        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;

        set<pair<int, int>> st;
        for (auto P : vec){
            auto [E, i] = P;
            if (cur == r)
                break;

            if (!E.second)
                st.insert({a[i][1], i});
            else{
                st.erase({a[i][1], i});
                if (i != cur) continue;
                if (st.empty()){
                    ans = -1;
                    break;
                }
                else{
                    auto it = st.upper_bound({a[r][1], r});
                    if (it == st.begin()){
                        ans = -1;
                        break;
                    }

                    it--;
                    cur = (*it).second;
                    ans++;
                }
            }
        }

        if (ans == -1){
            cout << "impossible\n";
            continue;
        }
        cout << ans << endl;
    }

    return 0;

    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 < que; 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;
        }

        if (a[cur][1] >= a[r][0]){
            cout << ans + 1 << '\n';
            continue;
        }

        if (a[cur][1] < a[r][0]){
            cout << "impossible\n";
            continue;
        }

        cout << ans + 1 << '\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