Submission #722641

#	Time	Username	Problem	Language	Result	Execution time	Memory
722641		dxz05	Event Hopping (BOI22_events)	C++17	10 / 100	1572 ms	3400 KiB

events

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
#define all(x) (x).begin(), (x).end()
#define MP make_pair
const int N = 100500;

int f[N];
int l[N], r[N];

bool can_switch(int i, int j){
    return l[j] <= r[i] && r[i] <= r[j];
}

void solve(){
    int n, q;
    cin >> n >> q;

    for (int i = 0; i < n; i++){
        cin >> l[i] >> r[i];
    }

    for (int i = 0; i < n; i++){
        f[i] = -1;
        for (int j = 0; j < n; j++){
            if (i == j) continue;
            if (can_switch(j, i)){
                if (f[i] == -1 || l[j] < l[f[i]]) f[i] = j;
            }
        }
        if (l[f[i]] >= l[i]) f[i] = -1;
    }

    while (q--){
        int x, y;
        cin >> x >> y;
        --x, --y;
        if (x == y){
            cout << 0 << endl;
            continue;
        }
        if (can_switch(x, y)){
            cout << 1 << endl;
            continue;
        }
        int cnt = 1;
        while (l[y] > r[x]){
            y = f[y];
            cnt++;
            if (y == -1) break;
        }

        if (y != -1 && can_switch(x, y)){
            cout << cnt << endl;
        } else {
            cout << "impossible" << endl;
        }
    }

}

int main() {
    ios_base::sync_with_stdio(false);

#ifdef LOCAL
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif

    solve();

    return 0;
}

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