Submission #919272

#	Time	Username	Problem	Language	Result	Execution time	Memory
919272		themm1	Event Hopping (BOI22_events)	C++17	100 / 100	393 ms	47568 KiB

events

#include <bits/stdc++.h>
using namespace std;
// ordered set whith s.order_of_key(x) method, which returns rank of element x in set s
/*
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
typedef tree<int, null_type, less_equal<int>, rb_tree_tag, tree_order_statistics_node_update> ordered_set;
*/

// pair printing
template <class T, class U>
ostream& operator<<(ostream& out, const pair<T, U> &par) {out << "(" << par.first << "; " << par.second << ")"; return out;}
// set printing
template <class T>
ostream& operator<<(ostream& out, const set<T> &cont) { out << "{"; for(const auto &x:cont) out << x << ", "; out << "}"; return out; }
// map printing
template <class T, class U>
ostream& operator<<(ostream& out, const map<T, U> &cont) {out << "{"; for(const auto &x:cont) out << x << ", "; out << "}"; return out; }
// unordered_set printing
template <class T>
ostream& operator<<(ostream& out, const unordered_set<T> &cont) {out << "{";for(const auto &x:cont) out << x << ", ";out << "}";return out;}
// unordered_map printing
template <class T, class U>
ostream& operator<<(ostream& out, const unordered_map<T, U> &cont) {out << "{";for(const auto &x:cont) out << x << ", ";out << "}";return out;}
// vector printing
template<class T>
ostream& operator<<(ostream& out, const vector<T> &cont){ out << "[";  for (const auto &x:cont) out << x << ", ";  out << "]"; return out;}

#define print(x) cout << (x) << endl;
#define dmp(x) cerr << #x << " = " << x << endl
#define dmpn(x) cerr << #x << " = " << x << "; "
#define dmpl(x) cerr << "Line " << __LINE__ << ": " << #x << " = " << x << endl

#define int long long
using ll = long long;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
#define pb push_back
#define ff first
#define ss second
#define all(x) begin(x), end(x)
#define sz(x) (int)x.size()
#define contains(s,x) ((s).find(x) != (s).end())
const int MOD = 998244353;

struct vertex {
        int idx, start, end, parent, depth;
        vector<int> children;
        vector<int> binjumps;
};

int N, Q, LG = 20;
vector<vertex> g;

int eval(int x) {
        if (x == INT_MAX) return INT_MAX;
        return g[x].start;
}

struct SegTree {
        int N;
        vector<int> tree;

        SegTree(vector<int> &base) {
                N = 1 << (32 - __builtin_clz(sz(base)));
                tree.assign(2 * N, INT_MAX);
                for (int i = 0; i < sz(base); i++) tree[N + i] = base[i];
                for (int i = N - 1; i > 0; i--) {
                        if (eval(tree[i * 2]) < eval(tree[i * 2 + 1])) tree[i] = tree[i * 2];
                        else tree[i] = tree[i * 2 + 1];
                }
                // dmp(tree);
        }

        int query(int l, int r, int i, int j, int idx) {
                if (l <= i && j <= r) {
                        return tree[idx];
                } else if ((i <= l && l < j) || (i < r && r <= j)) {
                        int mid = (i + j) / 2;
                        int x1 = query(l, r, i, mid, idx * 2);
                        int x2 = query(l, r, mid, j, idx * 2 + 1);
                        if (eval(x1) < eval(x2)) return x1;
                        else return x2;
                }
                return INT_MAX;
        }

        int bin_search_l(int base_row_idx, int mn) {
                int l = N, r = N + base_row_idx;
                while (r - l > 0) {
                        int mid = (l + r) / 2;
                        int val = g[tree[mid]].end;
                        if (val < mn) {
                                l = mid + 1;
                        } else {
                                r = mid;
                        }
                }
                return r - N;
        }
};

void dfs(int v, int p, int root, int depth) {
        g[v].depth = depth;

        g[v].binjumps.assign(LG, -1);
        g[v].binjumps[0] = p;
        for (int i = 1; i < LG; i++) {
                int last = g[v].binjumps[i - 1];
                if (last == -1) break;
                g[v].binjumps[i] = g[last].binjumps[i - 1];
        }
        for (int i = 0; i < LG; i++) if (g[v].binjumps[i] == -1) g[v].binjumps[i] = root;
        for (int u : g[v].children) if (u != p) {
                dfs(u, v, root, depth + 1);
        }
}

int relative_pos(int a, int b) {
        if (g[a].start <= g[b].end && g[b].end <= g[a].end) return 0;
        if (g[b].start <= g[a].end && g[a].end <= g[b].end) return 0;
        if (g[a].end < g[b].end) return 1;
        return -1;
}

void solve() {
        cin >> N >> Q;
        vector<pii> ends;
        for (int i = 0; i < N; i++) {
                int start, end;
                cin >> start >> end;
                g.pb({ i, start, end, -1 });
                ends.pb({ end, i });
        }
        sort(all(ends));
        vector<int> indices;
        for (pii pr : ends) indices.pb(pr.ss);
        SegTree st(indices);

        for (pii pr : ends) {
                int v = pr.ss;
                pii pr2 = { pr.ff, INT_MAX };
                int r = lower_bound(all(ends), pr2) - ends.begin() - 1;
                int l = st.bin_search_l(r, g[v].start);

                // dmpn(v); dmpn(l); dmp(r);
                if (l == r) continue;
                int parent = st.query(l, r + 1, 0, st.N, 1);
                if (g[parent].start < g[v].start) {
                        g[v].parent = parent;
                        g[parent].children.pb(v);
                }
        }

        for (int i = 0; i < N; i++) {
                // if is root
                if (g[i].parent == -1) dfs(i, -1, i, 0);
        }
        /*
        for (int i = 0; i < N; i++) {
                cout << i << ": ";
                for (int j : g[i].children) cout << j << ", ";
                cout << endl;
        }
        */
        while (Q--) {
                int s, e;
                cin >> s >> e;
                s--;
                e--;
                if (g[s].end > g[e].end) {
                        cout << "impossible" << endl;
                        continue;
                }

                int v = e, ans = INT_MAX;
                if (relative_pos(s, e) == 0) ans = 1;
                if (s == e) ans = 0;
                for (int k = LG - 1; k >= 0; k--) {
                        int anc = g[v].binjumps[k];
                        // dmpn(k); dmpn(v); dmp(anc);
                        int pos = relative_pos(s, anc);
                        // dmpn(k); dmp(anc);
                        if (pos == 1) {
                                v = anc;
                        } else if (pos == 0) {
                                int dist = g[e].depth - g[anc].depth;
                                if (s != anc) dist++;
                                // dmp(dist);
                                ans = min(ans, dist);
                        }
                }
                if (ans == INT_MAX) cout << "impossible" << endl;
                else cout << ans << endl;
        }
}

int32_t main() {
        ios::sync_with_stdio(false);
        cin.tie(0);
        cout.tie(0);

        int t = 1;
        // cin >> t;
        while (t--) {
                solve();
        }
}

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