Submission #721903

#	Time	Username	Problem	Language	Result	Execution time	Memory
721903		MDSPro	Event Hopping (BOI22_events)	C++14	30 / 100	151 ms	11916 KiB

events

#include "bits/stdc++.h"
 
using namespace std;

const int INF = 1e9;

int main(){
    cin.tie(0)->sync_with_stdio(0);
 
    int n,q; cin >> n >> q;
    vector<tuple<int,int,int>> ev;
    if(n <= 1000 && q <= 1000){
        for(int i = 0; i < n; ++i){
            int x,y; cin >> x >> y;
            ev.emplace_back(y,x,i+1);
        }

        sort(ev.begin(),ev.end());
    
        vector<int> nw_order(n+1);
        vector<int> left(n),right(n);
        for(int i = 0; i < n; ++i) {
            left[i] = get<1>(ev[i]);
            right[i] = get<0>(ev[i]);
            nw_order[get<2>(ev[i])] = i;
        }
        
        vector<vector<int>> g(n);
        for(int i = 0; i < n; ++i){
            for(int j = 0; j < n; ++j){
                if(i == j) continue;
                if(left[j] <= right[i] && right[i] <= right[j]) {
                    g[i].emplace_back(j);
                }
            }
        }

        auto get = [&](int a, int b){
            if(a == b) return 0;
            vector<int> dis(n,INF); dis[a] = 0;

            queue<int> q; q.push(a);
            while(!q.empty()){
                int mn = q.front(); q.pop();
                for(int z: g[mn]){
                    if(dis[z] == INF){
                        dis[z] = dis[mn]+1;
                        q.push(z);
                    }
                }
            }

            if(dis[b] == INF) return -1;
            else return dis[b];
        };

        while(q--){
            int a,b; cin >> a >> b;
            a = nw_order[a];
            b = nw_order[b];

            int dis = get(a,b);
            if(dis == -1) cout << "impossible\n";
            else cout << dis << '\n';
        }
    } else {
        for(int i = 0; i < n; ++i){
            int x,y; cin >> x >> y;
            ev.emplace_back(x,y,i+1);
        }

        sort(ev.begin(),ev.end());  
    
        vector<int> nw_order(n+1);
        vector<int> left(n),right(n);
        for(int i = 0; i < n; ++i) {
            left[i] = get<0>(ev[i]);
            right[i] = get<1>(ev[i]);
            nw_order[get<2>(ev[i])] = i;
        }
    
        vector<vector<int>> nxt(20,vector<int>(n+1));
        nxt[0][n] = n;
    
        int r = 0;
        for(int i = 0; i < n; ++i){
            while(r+1 < n && left[r+1] <= right[i]) r++;
    
            if(i != r) nxt[0][i] = r;
            else nxt[0][i] = n;
        }
        for(int i = 1; i < 20; ++i) {
            for(int j = 0; j <= n; ++j){
                nxt[i][j] = nxt[i-1][nxt[i-1][j]];
            }
        }
    
        auto get = [&](int x, int y){
            if(x == y) return 0;
            if(x > y) return -1;
            if(nxt[0][x] == n) return -1;
            if(nxt[0][x] > y) return 1;
    
            int cur = 0;
            for(int i = 19; i >= 0; --i){
                if(x == y) return cur;
                if(nxt[i][x] <= y) {
                    cur |= (1<<i);
                    x = nxt[i][x];
                }
            }
    
    
            if(x == y) return cur;
            if(nxt[0][x] == n) return -1;
            return cur+1;
        };
    
        while(q--){
            int a,b; cin >> a >> b;
            a = nw_order[a];
            b = nw_order[b];
    
            int ans = get(a,b);
            if(ans == -1) cout << "impossible\n";
            else cout << ans << '\n';
        }
    }
}

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