Submission #656553

#	Time	Username	Problem	Language	Result	Execution time	Memory
656553		Lobo	Event Hopping (BOI22_events)	C++17	25 / 100	1591 ms	6936 KiB

events

#include<bits/stdc++.h>
using namespace std;
const long long inf = (long long) 1e18 + 10;
const int inf1 = (int) 1e9 + 10;
#define int long long
#define dbl long double
#define endl '\n'
#define sc second
#define fr first
#define mp make_pair
#define pb push_back
#define all(x) x.begin(), x.end()

const int maxn = 1e5+10;

int n, q, idord[maxn], lf[maxn], rg[maxn], nx[maxn][25], pv[maxn][25];

void solve() {
    cin >> n >> q;
    vector<pair<pair<int,int>,int>> ord;
    vector<int> cc;
    for(int i = 1; i <= n; i++) {
        int l, r; cin >> l >> r;
        ord.pb(mp(mp(r,l),i));
        lf[i] = l;
        rg[i] = r;
        cc.pb(lf[i]);
        cc.pb(rg[i]);
    }
    sort(all(cc));
    cc.erase(unique(all(cc)),cc.end());
    for(int i = 1; i <= n; i++) {
        lf[i] = upper_bound(all(cc),lf[i])-cc.begin();
        rg[i] = upper_bound(all(cc),rg[i])-cc.begin();
    }
    // sort(all(ord));

    for(int i = 1; i <= n; i++) {
        nx[i][0] = 0;
        for(int j = 1; j <= n; j++) {
            if(j == i || !(lf[j] <= rg[i] && rg[i] <= rg[j]) || !(rg[j] > rg[i])) continue;
            if(nx[i][0] == 0 || rg[j] > rg[nx[i][0]]) nx[i][0] = j;
        }
        pv[i][0] = 0;
        for(int j = 1; j <= n; j++) {
            if(j == i || !(lf[i] <= rg[j] && rg[j] <= rg[i]) || !(lf[j] < lf[i])) continue;
            if(pv[i][0] == 0 || lf[j] < lf[pv[i][0]]) pv[i][0] = j;
        }
        // int l = i+1;
        // int r = n;
        // while(l <= r) {
        //     int mid = (l+r)/2;
        //     if(lf[mid] <= rg[i]) {
        //         nx[i][0] = mid;
        //         l = mid+1;
        //     }
        //     else {
        //         r = mid-1;
        //     }
        // }

        // cout << i << " " << nx[i][0] << " " << pv[i][0] << endl;
    }

    for(int j = 1; j <= 20; j++) {
        for(int i = 1; i <= n; i++) {
            nx[i][j] = nx[nx[i][j-1]][j-1];
            pv[i][j] = pv[pv[i][j-1]][j-1];
        }
    }

    while(q--) {
        int s,e; cin >> s >> e;

        int ans = 0;
        for(int j = 20; j >= 0; j--) {
            if(nx[s][j] != 0 && rg[nx[s][j]] < rg[e]) {
                ans+= (1<<j);
                s = nx[s][j];
            }
        }
        for(int j = 20; j >= 0; j--) {
            if(pv[e][j] != 0 && lf[pv[e][j]] > lf[s]) {
                ans+= (1<<j);
                e = pv[e][j];
            }
        }
        if(s == e) {
            cout << ans << endl;
        }
        else if(lf[e] <= rg[s] && rg[s] <= rg[e]) {
            cout << ans+1 << endl;
        }
        else if(nx[s][0] != 0 && lf[e] <= rg[nx[s][0]] && rg[nx[s][0]] <= rg[e]) {
            cout << ans+2 << endl;
        }
        else if(pv[e][0] != 0 && lf[pv[e][0]] <= rg[s] && rg[s] <= rg[pv[e][0]]) {
            cout << ans+2 << endl;
        }
        else {
            cout << "impossible" << endl;
        }
    }
}

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

    // freopen("in.in", "r", stdin);
    // freopen("out.out", "w", stdout);
    int tt = 1;
    // cin >> tt;
    while(tt--) {
        solve();
    }

}

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