Submission #1094703

#	Time	Username	Problem	Language	Result	Execution time	Memory
1094703		crafticat	Event Hopping (BOI22_events)	C++17	0 / 100	168 ms	16324 KiB

events

#include "bits/stdc++.h"

using namespace std;
template<typename T>
using V = vector<T>;
using vi = V<int>;
using pi = pair<int,int>;
#define f first
#define s second

#define F0R(i, n) for(int i = 0; i < n;i++)
#define FOR(i,a, n) for(int i = a; i < n;i++)
#define pb push_back
#define all(x) begin(x), end(x)
#define each(x, y) for(auto &x : y)

#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
template <class T>
using Tree =
        tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
constexpr int INF = 1e9 + 2;

pi binarySearch(V<pi> &stack, int point) {
    auto it = std::upper_bound(stack.begin(), stack.end(), make_pair(point,INF)); // Point to before or at point
    if (it == stack.begin()) return {0,0};
    it--;
    return {it - stack.begin() + 1, it->s};
}

int getImp(V<pi> &stack) {
    return (stack.empty() ? 0 : stack.back().s);
}

int main() {
    int n, q; cin >> n >> q;

    V<pair<pi, int>> edges;
    map<int, V<pi>> queries;
    V<int> ans(q, -1);

    F0R(i, n) {
        int a, b; cin >> a >> b;
        edges.pb({{b, a},i});
    }
    F0R(i, q) {
        int a, b; cin >> a >> b;
        a--;
        b--;
        queries[b].push_back({edges[a].f.f,i});
    }
    sort(all(edges));

    V<pi> stack; // Point, possible prefix
    // Self bug?
    // Note not efficient if q(s).size == n

    each(edgeDATA, edges) {
        auto [edge, id] = edgeDATA;
        swap(edge.f, edge.s);
        pi last = {-1,-1};

        while (!stack.empty() && stack.back().f >= edge.f) {
            last = stack.back();
            stack.pop_back();
        }

        if (last.f != -1) stack.push_back(last);
        stack.emplace_back(edge.s, getImp(stack)  + (last.f == -1 ? 1 : 0));

        each(starts, queries[id]) {
            auto data = binarySearch(stack, starts.f);
            if (getImp(stack) - data.s > 0) continue;
            ans[starts.s] = stack.size() - data.f;
        }
    }

    F0R(i, q) {
        if (ans[i] == -1) cout << "impossible\n";
        else cout << ans[i] << "\n";
    }

    return 0;
}

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