Submission #904809

#	Time	Username	Problem	Language	Result	Execution time	Memory
904809		LOLOLO	Event Hopping (BOI22_events)	C++17	100 / 100	178 ms	22452 KiB

events

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

#define           f     first
#define           s     second
#define           pb    push_back
#define           ep    emplace
#define           eb    emplace_back
#define           lb    lower_bound
#define           ub    upper_bound
#define       all(x)    x.begin(), x.end()
#define      rall(x)    x.rbegin(), x.rend()
#define   uniquev(v)    sort(all(v)), (v).resize(unique(all(v)) - (v).begin())
#define     mem(f,x)    memset(f , x , sizeof(f))
#define        sz(x)    (int)(x).size()
#define  __lcm(a, b)    (1ll * ((a) / __gcd((a), (b))) * (b))
#define          mxx    *max_element
#define          mnn    *min_element
#define    cntbit(x)    __builtin_popcountll(x)
#define       len(x)    (int)(x.length())

const int N = 2e5 + 10;
pair <int, int> seg[N * 4];

void upd(int id, int l, int r, int p, pair <int, int> st) {
    if (l > p || r < p)
        return;

    if (l == r) {
        seg[id] = min(seg[id], st);
        return;
    }

    int m = (l + r) / 2;
    upd(id * 2, l, m, p, st);
    upd(id * 2 + 1, m + 1, r, p, st);
    seg[id] = min(seg[id * 2], seg[id * 2 + 1]);
}

pair <int, int> get(int id, int l, int r, int u, int v) {
    if (l > v || r < u)
        return make_pair(1e8, 0);

    if (l >= u && r <= v)
        return seg[id];

    int m = (l + r) / 2;
    return min(get(id * 2, l, m, u, v), get(id * 2 + 1, m + 1, r, u, v));
}

int l[N], r[N];
pair <int, int> save[N];
int sp[N][20];

ll solve() {
    for (int i = 1; i < N * 4; i++)
        seg[i] = make_pair(1e9, 0);

    int n, q;
    cin >> n >> q;

    vector <int> save;
    for (int i = 1; i <= n; i++) {
        cin >> l[i] >> r[i];
        save.pb(l[i]);
        save.pb(r[i]);
    }

    uniquev(save);
    for (int i = 1; i <= n; i++) {
        l[i] = lower_bound(all(save), l[i]) - save.begin() + 1;
        r[i] = lower_bound(all(save), r[i]) - save.begin() + 1;
        upd(1, 1, N, r[i], make_pair(l[i], i));
    }

    for (int i = 1; i <= n; i++) {
        sp[i][0] = get(1, 1, N, l[i], r[i]).s;
    }

    for (int j = 1; j < 20; j++) {
        for (int i = 1; i <= n; i++) {
            sp[i][j] = sp[sp[i][j - 1]][j - 1];
        }
    }

    while (q--) {
        int a, b;
        cin >> a >> b;

        if (a == b) {
            cout << 0 << '\n';
            continue;
        }

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

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

        int ans = 0;
        for (int i = 19; i >= 0; i--) {
            if (r[a] < l[sp[b][i]]) {
                ans |= (1 << i);
                b = sp[b][i];
            }
        }

        if (ans > N) {
            cout << "impossible\n";
            continue;
        }

        cout << ans + 2 << '\n';
    }
    return 0;
}

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

    int t = 1;
    //cin >> t;

    while (t--) {
        solve();
        //cout << solve() << '\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