Submission #1026488

#	Time	Username	Problem	Language	Result	Execution time	Memory
1026488		gyg	Event Hopping (BOI22_events)	C++17	0 / 100	76 ms	26084 KiB

events

#pragma GCC optimize("O3", "unroll-loops")
#pragma GCC target("avx2")
#include <bits/stdc++.h>    
using namespace std;
using pii = pair<int, int>;
const int MAX_N = 1e5 + 5, INF = 1e9;

int n, q;
array<int, MAX_N> l, r;

vector<pii> ord; // {r, i}
int n_ccs;
unordered_map<int, int> cc;
array<int, MAX_N> cc_l, cc_r;
void precomp() {
    for (int i = 1; i <= n; i++) ord.push_back({r[i], i});
    sort(ord.rbegin(), ord.rend());

    set<int> coords;
    for (int i = 1; i <= n; i++) coords.insert(l[i]), coords.insert(r[i]);
    while (coords.size()) {
        n_ccs++, cc[*coords.begin()] = n_ccs;
        coords.erase(coords.begin());
    }

    for (int i = 1; i <= n; i++) cc_l[i] = cc[l[i]], cc_r[i] == cc[r[i]];
}

array<int, 8 * MAX_N> st;
void update(int l, int r, int x, int u = 1, int lo = 1, int hi = n_ccs) {
    if (l <= lo && hi <= r) { st[u] = min(st[u], x); return; }
    int mid = (lo + hi) / 2;
    if (l <= mid) update(l, r, x, 2 * u, lo, mid); 
    if (r > mid) update(l, r, x, 2 * u + 1, mid + 1, hi);
}
int query(int i, int u = 1, int lo = 1, int hi = n_ccs) {
    if (lo == hi) return st[u];
    int mid = (lo + hi) / 2;
    if (i <= mid) return min(st[u], query(i, 2 * u, lo, mid));
    else return min(st[u], query(i, 2 * u + 1, mid + 1, hi));
}

array<int, MAX_N> dp;
void comp(int f) {
    fill(st.begin() + 1, st.end() + 4 * n_ccs, INF);

    for (pii x : ord) {
        int i = x.second;
        if (i == f) dp[i] = 0;
        else if (l[f] <= r[i] && r[i] <= r[f]) dp[i] = 1;
        else dp[i] = query(cc_r[i]) + 1;
        update(cc_l[i], cc_r[i], dp[i]);
    }
} 

int main() {
    // freopen("event.in", "r", stdin);
    cin.sync_with_stdio(false), cin.tie(0);

    cin >> n >> q;
    for (int i = 1; i <= n; i++) cin >> l[i] >> r[i];
    
    precomp();

    for (int i = 1; i <= q; i++) {
        int s, f; cin >> s >> f;
        comp(f);
        if (dp[s] >= INF) cout << "impossible" << '\n';
        else cout << dp[s] << '\n';
    }
}

Compilation message (stderr)

events.cpp: In function 'void precomp()':
events.cpp:26:62: warning: value computed is not used [-Wunused-value]
   26 |     for (int i = 1; i <= n; i++) cc_l[i] = cc[l[i]], cc_r[i] == cc[r[i]];

• Subtask 1: 0 / 10
• Subtask 2: 0 / 10
• Subtask 3: 0 / 15
• Subtask 4: 0 / 15
• Subtask 5: 0 / 20
• Subtask 6: 0 / 30