Submission #1172062

#	Time	Username	Problem	Language	Result	Execution time	Memory
1172062		yoav_s	Event Hopping (BOI22_events)	C++20	100 / 100	276 ms	42468 KiB

events

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef vector<ll> v;
typedef vector<v> vv;
typedef vector<vv> vvv;
typedef pair<ll, ll> p;
typedef vector<p> vp;
typedef vector<vp> vvp;
typedef vector<vvp> vvvp;
typedef pair<ll, p> tri;
typedef vector<tri> vtri;
typedef vector<vtri> vvtri;
typedef vector<vvtri> vvvtri;
typedef vector<bool> vb;
typedef vector<vb> vvb;
typedef vector<vvb> vvvb;

#define f first
#define s second
#define pb push_back
#define eb emplace_back
#define all(v) (v).begin(),(v).end()

const ll INF = 1e18;
const ll mod = 1e9 + 7;

ll query(vp &st, ll l, ll r)
{
    l += st.size() / 2;
    r += st.size() / 2;
    ll bestIndex, best = INF;
    while (l <= r)
    {
        if (l % 2 == 1)
        {
            if (st[l].f < best)
            {
                best = st[l].f;
                bestIndex = st[l].s;
            }
            l++;
        }
        if (r % 2 == 0)
        {
            if (st[r].f < best)
            {
                best = st[r].f;
                bestIndex = st[r].s;
            }
            r--;
        }
        l /= 2; r /= 2;
    }
    return bestIndex;
}

int main()
{
    ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
    ll N, Q;
    cin >> N >> Q;
    vp events(N);
    for (ll i = 0; i < N; i++) cin >> events[i].f >> events[i].s;
    v numbers;
    for (ll i = 0; i < N; i++)
    {
        numbers.pb(events[i].f);
        numbers.pb(events[i].s);
    }
    sort(all(numbers)); numbers.erase(unique(all(numbers)),numbers.end());
    map<ll, ll> shrink;
    for (ll i = 0; i < numbers.size(); i++) shrink[numbers[i]] = i;
    for (ll i = 0; i < N; i++)
    {
        events[i].f = shrink[events[i].f];
        events[i].s = shrink[events[i].s];
    }
    ll m = numbers.size();
    ll n = pow(2, ceil(log2(m)));
    vp st(2 * n, p(INF, -1));
    for (ll i = 0; i < N; i++) if (events[i].f < st[n + events[i].s].f) st[n + events[i].s] = p(events[i].f, i);
    for (ll i = n - 1; i > 0; i--)
    {
        if (st[2 * i].f < st[2 * i + 1].f)  st[i] = st[2 * i];
        else st[i] = st[2 * i + 1];
    }
    v prev(N);
    for (ll curEvent = 0; curEvent < N; curEvent++)
    {
        ll bestEvent = query(st, events[curEvent].f, events[curEvent].s);
        //TODO check if worse than curEvent
        prev[curEvent] = bestEvent;
    }
    ll logN = log2(N);
    vv prevLifting(N, v(logN + 1, -1));
    for (ll i = 0; i < N; i++) prevLifting[i][0] = prev[i];
    for (ll j = 1; j <= logN; j++)
    {
        for (ll i = 0; i < N; i++)
        {
            prevLifting[i][j] = prevLifting[prevLifting[i][j - 1]][j - 1];
        }
    }
    while (Q--)
    {
        ll s, e;
        cin >> s >> e; s--; e--;
        if (s == e)
        {
            cout << "0\n";
            continue;
        }
        if (events[s].s > events[e].s)
        {
            cout << "impossible\n";
            continue;
        }
        if (events[e].f <= events[s].s && events[e].s >= events[s].s)
        {
            cout << "1\n";
            continue;
        }
        ll curEvent = e;
        ll hops = 0;
        for (ll j = logN; j >= 0; j--)
        {
            ll next = prevLifting[curEvent][j];
            if (events[s].s < events[next].f)
            {
                curEvent = next;
                hops += (1 << j);
            }
        }
        curEvent = prev[curEvent]; hops++;
        if (events[s].s >= events[curEvent].f)
        {
            cout << hops + 1 << "\n";
            continue;
        }
        cout << "impossible\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