Submission #864218

#	Time	Username	Problem	Language	Result	Execution time	Memory
864218		danikoynov	Event Hopping (BOI22_events)	C++14	0 / 100	1580 ms	3756 KiB

events

#include<bits/stdc++.h>

using namespace std;

const int maxn = 1e5 + 10;
     
struct interval
{
    int s, e, idx;
}seg[maxn];
     
int n, q;   
pair < int, int > task[maxn];

void input()
{
    cin >> n >> q;
    for (int i = 1; i <= n; i ++)
    {
        cin >> seg[i].s >> seg[i].e;
        seg[i].idx = i;
    }
    for (int i = 1; i <= q; i ++)
    {
        cin >> task[i].first >> task[i].second;
    }
}


bool cmp_end(interval seg1, interval seg2)
{
    
    return seg1.e < seg2.e;
}

int lf[maxn], rev[maxn], rf[maxn];
void build_graph()
{
    sort(seg + 1, seg + n + 1, cmp_end);
    for (int i = 1; i <= n; i ++)
    {
        rev[seg[i].idx] = i;
    }

    for (int i = 1; i <= n; i ++)
    {
        lf[i] = 1;
        while(seg[lf[i]].e < seg[i].s)
            lf[i] ++;

        rf[i] = n;
        while(seg[rf[i]].e > seg[i].e)
            rf[i] --;
    }
}

void answer_queries()
{
    /**cout << "----------------------" << endl;
    for (int i = 1; i <= n; i ++)
        cout << seg[i].s << " :: " << seg[i].e << endl;*/
    
    for (int i = 1; i <= q; i ++)
    {
        int st = rev[task[i].first], en = rev[task[i].second];
        if (st > en)
        {
            cout << "impossible" << endl;
            continue;
        }

        int steps = 0, last_left = en + 1, last_right = en - 1;
        int bound_left = en, bound_right = en;
        bool done = false;
        while(!(st >= bound_left && st <= bound_right))
        {
            ///cout << last << " " << bound << endl;
            steps ++;
            int new_left = bound_left;
            int new_right = bound_right;
            for (int i = bound_left; i < last_left; i ++)
            {
                new_left = min(new_left, lf[i]);
                new_right = max(new_right, rf[i]);
            }
            for (int i = last_right + 1; i <= bound_right; i ++)
            {
                new_left = min(new_left, lf[i]);
                new_right = max(new_right, rf[i]);
            }
            ///cout << new_bound << endl;
            if (new_left == bound_left && new_right == bound_right)
            {
                done = true;
                break;
            }
            
            last_left = bound_left;
            last_right = bound_right;
            bound_left = new_left;
            bound_right = new_right;
        }

        if (done)
            cout << "impossible" << endl;
        else
            cout << steps << endl;
    }
}
void solve()
{  
    input();
    build_graph();
    answer_queries();
}

int main()
{   
    ///speed();
    solve();

    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