Submission #838689

#	Time	Username	Problem	Language	Result	Execution time	Memory
838689		skittles1412	Event Hopping (BOI22_events)	C++17	25 / 100	1581 ms	8156 KiB

events

#include "bits/extc++.h"

using namespace std;

template <typename T, typename... U>
void dbgh(const T& t, const U&... u) {
    cerr << t;
    ((cerr << " | " << u), ...);
    cerr << endl;
}

#ifdef DEBUG
#define dbg(...)                                              \
    cerr << "L" << __LINE__ << " [" << #__VA_ARGS__ << "]: "; \
    dbgh(__VA_ARGS__)
#else
#define dbg(...)
#define cerr   \
    if (false) \
    cerr
#endif

#define endl "\n"
#define long int64_t
#define sz(x) int(std::size(x))

void solve() {
    int n, q;
    cin >> n >> q;

    vector<pair<int, int>> arr(n);
    for (auto& [l, r] : arr) {
        cin >> l >> r;
    }

    int logn = __lg(n);

    vector<vector<int>> lift(logn + 1, vector<int>(n));
    for (int i = 0; i < n; i++) {
        pair<int, int> c_opt {int(1e9), -1};

        for (int j = 0; j < n; j++) {
            if (arr[i].first <= arr[j].second &&
                arr[j].second <= arr[i].second) {
                c_opt = min(c_opt, {arr[j].first, j});
            }
        }

        if (c_opt.first >= arr[i].first) {
            lift[0][i] = -1;
        } else {
            lift[0][i] = c_opt.second;
        }
    }

    for (int i = 1; i <= logn; i++) {
        for (int j = 0; j < n; j++) {
            if (lift[i - 1][j] == -1) {
                lift[i][j] = -1;
            } else {
                lift[i][j] = lift[i - 1][lift[i - 1][j]];
            }
        }
    }

    while (q--) {
        int u, v;
        cin >> u >> v;
        u--;
        v--;

        if (u == v) {
            cout << 0 << endl;
            continue;
        }

        int ans = 0;
        for (int i = logn; i >= 0; i--) {
            int nv = lift[i][v];
            if (nv != -1 && arr[u].second < arr[nv].first) {
                v = nv;
                ans += 1 << i;
            }
        }
        if (arr[u].second < arr[v].first) {
            v = lift[0][v];
            ans++;
        }
        // int ql = arr[v].first, qr = arr[v].second, ans = 0;

        // while (ql > arr[u].second) {
        //     int n_opt = 1e9;

        //     for (auto& [l, r] : arr) {
        //         if (ql <= r && r <= qr) {
        //             n_opt = min(n_opt, l);
        //         }
        //     }

        //     if (n_opt >= ql) {
        //         break;
        //     }
        //     ans++;
        //     ql = n_opt;
        // }

        if (v != -1 && arr[v].first <= arr[u].second &&
            arr[u].second <= arr[v].second) {
            ans++;
            cout << ans << endl;
        } else {
            cout << "impossible" << endl;
        }
    }
}

int main() {
    cin.tie(nullptr);
    cin.exceptions(ios::failbit);
    ios_base::sync_with_stdio(false);
    solve();
}

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