Submission #850077

#	Time	Username	Problem	Language	Result	Execution time	Memory
850077		MinaRagy06	Event Hopping (BOI22_events)	C++17	100 / 100	335 ms	75252 KiB

events

#include <bits/stdc++.h>
#define md ((l + r) >> 1)
using namespace std;
typedef int64_t ll;
 
const int N = 200'005;
array<int, 2> a[N];
int bl[18][N], bl2[18][N];
vector<array<int, 2>> st[2 * N], en[2 * N];
struct node {
    pair<int, int> mn;
    node() {mn = {1e9, -1};}
    node(pair<int, int> _mn) {mn = _mn;}
    friend node operator+(const node &l, const node &r) {
        return min(l.mn, r.mn);
    }
} seg[1 << 19];
void upd(int i, int l, int r, int x, pair<int, int> v) {
    if (x == l && r == x) {
        seg[i].mn = min(seg[i].mn, v);
        return;
    }
    if (r < x || x < l) {
        return;
    }
    upd(i << 1, l, md, x, v);
    upd(i << 1 | 1, md + 1, r, x, v);
    seg[i] = seg[i << 1] + seg[i << 1 | 1];
}
node get(int i, int l, int r, int s, int e) {
    if (s <= l && r <= e) {
        return seg[i];
    }
    if (r < s || e < l) {
        return node();
    }
    return get(i << 1, l, md, s, e) + get(i << 1 | 1, md + 1, r, s, e);
}
int main() {
    ios_base::sync_with_stdio(0), cin.tie(0);
    int n, q;
    cin >> n >> q;
    set<int> times;
    for (int i = 0; i < n; i++) {
        cin >> a[i][0] >> a[i][1];
        times.insert(a[i][0]), times.insert(a[i][1]);
    }
    vector<int> v;
    for (auto i : times) {
        v.push_back(i);
    }
    for (int i = 0; i < n; i++) {
        st[lower_bound(v.begin(), v.end(), a[i][0]) - v.begin()].push_back({i, a[i][1]});
        en[lower_bound(v.begin(), v.end(), a[i][1]) - v.begin()].push_back({i, a[i][1]});
    }
    multiset<array<int, 2>> s;
    for (int i = v.size() - 1; i >= 0; i--) {
        for (auto [idx, t] : en[i]) {
            s.insert({-t, idx});
        }
        for (auto [idx, t] : en[i]) {
            bl[0][idx] = (*s.begin())[1];
        }
        for (auto [idx, t] : st[i]) {
            s.erase(s.find({-t, idx}));
        }
    }
    for (int j = 1; j < 18; j++) {
        for (int i = 0; i < n; i++) {
            bl[j][i] = bl[j - 1][bl[j - 1][i]];
        }
    }
    s.clear();
    for (int i = 0; i < v.size(); i++) {
        st[i].clear();
        en[i].clear();
    }
    for (int i = 0; i < n; i++) {
        int pos = lower_bound(v.begin(), v.end(), a[i][1]) - v.begin();
        upd(1, 0, v.size() - 1, pos, {a[i][0], i});
    }
    for (int i = 0; i < n; i++) {
        int l = lower_bound(v.begin(), v.end(), a[i][0]) - v.begin();
        int r = lower_bound(v.begin(), v.end(), a[i][1]) - v.begin();
        bl2[0][i] = get(1, 0, v.size() - 1, l, r).mn.second;
    }
    for (int j = 1; j < 18; j++) {
        for (int i = 0; i < n; i++) {
            bl2[j][i] = bl2[j - 1][bl2[j - 1][i]];
        }
    }
    /*
    for (int i = 0; i < n; i++) {

        cout << bl2[0][i] << ' ';
    }
    cout << '\n';*/
    while (q--) {
        int s, e;
        cin >> s >> e;
        s--, e--;
        if (s == e) {
            cout << "0\n";
            continue;
        }
        if (a[e][0] <= a[s][1] && a[s][1] <= a[e][1]) {
            cout << "1\n";
            continue;
        }
        int ans = 0;
        for (int j = 17; j >= 0; j--) {
            int New = bl[j][s];
            if (!(a[e][0] <= a[New][1] && a[New][1] <= a[e][1]) && a[New][1] <= a[e][1]) {
                s = New;
                ans += (1 << j);
            }
        }
        if (a[bl[0][s]][1] > a[e][1]) {
            for (int j = 17; j >= 0; j--) {
                int New = bl2[j][e];
                if (!(a[New][0] <= a[s][1] && a[s][1] <= a[New][1]) && a[s][1] <= a[New][1]) {
                    e = New;
                    ans += 1 << j;
                }
            }
            ans++;
            e = bl2[0][e];
        } else {
            ans++;
            s = bl[0][s];
        }
        if (!(a[e][0] <= a[s][1] && a[s][1] <= a[e][1])) {
            cout << "impossible\n";
            continue;
        }
        cout << ans + 1 << '\n';
    }
    return 0;
}

Compilation message (stderr)

events.cpp: In function 'int main()':
events.cpp:74:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   74 |     for (int i = 0; i < v.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