Submission #779665

#	Time	Username	Problem	Language	Result	Execution time	Memory
779665		CpDark	Event Hopping (BOI22_events)	C++14	100 / 100	159 ms	19048 KiB

events

#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int, int> pii;
typedef vector<pii> vp;
typedef vector<vp> vvp;
typedef vector<bool> vb;
typedef vector<vb> vvb;
typedef vector<ll> vll;
typedef vector<vll> vvll;

const int inf = 1e9 + 7;

struct segmentTree
{
    vp st;
    int size;
    segmentTree() {};
    void init(int n) {
        for (size = 1;size < n;size *= 2) {}
        st.resize(size * 2, { inf, -1 });
    }

    void update(int i, pii val) {
        i += size;
        if (st[i].first <= val.first)return;
        st[i] = val;
        for (i /= 2;i;i /= 2) {
            if (st[i * 2].first <= st[i * 2 + 1].first) {
                st[i] = st[i * 2];
            }
            else st[i] = st[i * 2 + 1];
        }
    }

    pii query(int l, int r) {
        pii ans = { inf,0 };
        for (l += size, r += size;l <= r;l /= 2, r /= 2) {
            if (l % 2) {
                if (ans.first > st[l].first)ans = st[l];
                l++;
            }
            if (r % 2 == 0) {
                if (ans.first > st[r].first)ans = st[r];
                r--;
            }
        }
        return ans;
    }
};

vi times;
vvi table;
vp events;
vector<pair<int, pii>> endTimes;

int mylog;

int query(int start, int end) {
    if (start == end)return 0;
    if (events[start].second > events[end].second)return -1;
    int wall = events[start].second;
    int jumps = 1;
    if (events[end].first <= wall && wall <= events[end].second) return jumps;
    
    for (int i = mylog;i >= 0;i--) {
        if (events[table[i][end]].first > wall) {
            jumps += 1 << i;
            end = table[i][end];
        }
    }
    jumps++;
    end = table[0][end];
    if (events[end].first <= wall && wall <= events[end].second)return jumps;
    return -1;
}

int id(int val) {
    int ans = lower_bound(times.begin(), times.end(), val) - times.begin();
    return ans;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    
    int n, q;
    cin >> n >> q;
    mylog = ceil(log2(n + 1));
    events.resize(n);
    endTimes.resize(n);
    table.resize(mylog + 1, vi(n));
    
    for (int i = 0;i < n;i++) {
        cin >> events[i].first >> events[i].second;
        times.push_back(events[i].first);
        times.push_back(events[i].second);
        endTimes[i] = { events[i].second, {events[i].first, i} };
    }
    times.push_back(inf);

    sort(times.begin(), times.end());
    sort(endTimes.begin(), endTimes.end());

    segmentTree st;
    st.init(times.size());
    for (int i = 0;i < endTimes.size();i++) {
        int index = endTimes[i].second.second;
        st.update(id(events[index].second), { events[index].first, index });
        int far = st.query(id(events[index].first), id(events[index].second)).second;
        table[0][index] = far;
    }
 
    for (int i = 1;i <= mylog;i++) {
        for (int v = 0;v < n;v++) {
            int p = table[i - 1][v];
            table[i][v] = table[i - 1][p];
        }
    }
 
    int s, e;
    for (int i = 0;i < q;i++) {
        cin >> s >> e;
        s--; e--;
        int ans = query(s, e);
        if (ans == -1) {
            cout << "impossible\n";
        }
        else {
            cout << ans << '\n';
        }
    }
 
    return 0;
}

Compilation message (stderr)

events.cpp: In function 'int main()':
events.cpp:110:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, std::pair<int, int> > >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  110 |     for (int i = 0;i < endTimes.size();i++) {
      |                    ~~^~~~~~~~~~~~~~~~~

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