Submission #987405

#	Time	Username	Problem	Language	Result	Execution time	Memory
987405		makrav	Event Hopping (BOI22_events)	C++14	100 / 100	264 ms	118636 KiB

events

#include <bits/stdc++.h>

using namespace std;
using ll = long long;
using ld = long double;

#define all(a) (a).begin(), (a).end()
#define sz(a) (int) a.size()
#define pb push_back
#define ff first
#define sc second
#define pii pair<int, int>
#define f(i, l, r) for (int i = (l); i < (r); i++)
#define double ld

int sp[18][18][100010];

signed main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int n, q; cin >> n >> q;
    vector<array<int, 3>> a(n);
    for (int i = 0; i < n; i++) {
        cin >> a[i][0] >> a[i][1];
        a[i][2] = i;
    }
    sort(all(a), [](array<int, 3> x, array<int, 3> y) {
        return x[1] < y[1];
    });

    vector<vector<int>> up(18, vector<int>(n, 0));
    vector<int> nxt(n);
    int prv = n - 1;
    for (int i = n - 1; i >= 0; i--) {
        if (i == n - 1 || a[i][1] == a[i + 1][1]) nxt[i] = prv;
        else {
            prv = i;
            nxt[i] = prv;
        }
        int L = -1, R = n;
        while (R - L > 1) {
            int M = (L + R) / 2;
            if (a[M][1] >= a[i][0]) R = M;
            else L = M;
        }
        up[0][i] = R;
    }
    auto req = [&](int lvl, int l, int r) {
        int lg = (int)log2(r - l + 1);
        return min(sp[lvl][lg][l], sp[lvl][lg][r - (1 << lg) + 1]);
        };
    for (int lvl = 1; lvl < 18; lvl++) {
        for (int j = 0; j < n; j++) sp[lvl - 1][0][j] = up[lvl - 1][j];
        for (int i = 1; i < 18; i++) {
            for (int j = 0; j + (1 << i) - 1 < n; j++) {
                sp[lvl - 1][i][j] = min(sp[lvl - 1][i - 1][j], sp[lvl - 1][i - 1][j + (1 << (i - 1))]);
            }
        }
        
        for (int i = 0; i < n; i++) {
            up[lvl][i] = req(lvl - 1, up[lvl - 1][i], nxt[i]);
        }
    }
    vector<int> pos(n);
    for (int i = 0; i < n; i++) pos[a[i][2]] = i;
    while (q--) {
        int s, e; cin >> s >> e;
        s--; e--;
        s = pos[s];
        e = pos[e];
        if (a[s][1] > a[e][1]) {
            cout << "impossible\n";
            continue;
        }
        if (s == e) {
            cout << "0\n";
            continue;
        }
        int curr = e, curl = e, ans = 0;
        for (int j = 17; j >= 0; j--) {
            if (a[req(j, curl, curr)][1] > a[s][1]) {
                ans += (1 << j);
                curl = req(j, curl, curr);
                curr = nxt[e];
            }
        }
        if (ans > n) cout << "impossible\n";
        else cout << ans + 1 << '\n';
    }

    return 0;
}

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