Submission #1346985

#TimeUsernameProblemLanguageResultExecution timeMemory
1346985KindaGoodGamesEvent Hopping (BOI22_events)C++20
0 / 100
268 ms589824 KiB
#pragma GCC optimize("O3,unroll-loops,Ofast")
#include<bits/stdc++.h>


#define ll long long
#define pii pair<int,int>
#define tiii tuple<int,int,int>

using namespace std;

int INF = numeric_limits<int>::max()/2;

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    int n,q;
    cin >> n >> q;

    vector<pii>arr(n);
    vector<tiii>carr(n);

    for(int i = 0; i < n; i++){
        int a,b;
        cin >> a >>b;
        arr[i] = {a,b};
        carr[i] = {a,b,i};
    }

    sort(carr.begin(),carr.end(), [](tiii a, tiii b){return get<1>(a) < get<1>(b);});
    sort(arr.begin(),arr.end(), [](pii a, pii b){return a.first < b.second;});
    vector<int> newInd(n);
    for(int i = 0; i < n; i++){
        newInd[get<2>(carr[i])] = i;
    } 

    vector<vector<int>> ans(n,vector<int>(n,INF));

    for(int i = n-1; i >= 0; i--){
        int pt = n; 
        set<pii> cur;
        priority_queue<tiii> active;
        cur.insert({0,i});
        active.push({get<0>(arr[i]),i,0});
        ans[i][i] = 0;

        while(--pt >= 0){
            if(pt == i) continue;
            if(arr[pt].second > arr[i].second) continue;
            while(active.size() && get<0>(active.top()) > arr[pt].second){
                int st, c, ind;
                tie(st, ind,c) = active.top(); active.pop();
                cur.erase({c,ind});
            }

            if(cur.size()) ans[pt][i] = (*cur.begin()).first+1;
            else break;

            cur.insert({ans[pt][i], pt});
            active.push({arr[pt].first, pt, ans[pt][i]});
        }
    }

    while(q--){
        int s,t;
        cin >> s >> t;
        s--;t--;
        s = newInd[s];
        t = newInd[t];

        if(ans[s][t] >= INF){
            cout << "impossible\n";
            continue;
        }else{
            cout << ans[s][t] << "\n";
        }
    }
}
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