Submission #864175

#	Time	Username	Problem	Language	Result	Execution time	Memory
864175		vnm06	Event Hopping (BOI22_events)	C++14	20 / 100	101 ms	12368 KiB

events

#include<bits/stdc++.h>
#define endl '\n'

using namespace std;

int n, q;
int doseg[100005];
int tree[400005];

void update(int v, int le, int ri, int pos)
{
    if(le==ri) tree[v]=pos;
    else
    {
        int mid=(le+ri)/2;
        if(pos<=mid) update(2*v, le, mid, pos);
        else update(2*v+1, mid+1, ri, pos);
        if(doseg[tree[2*v]]<doseg[tree[2*v+1]]) tree[v]=tree[2*v];
        else tree[v]=tree[2*v+1];
    }
}

int query(int v, int le, int ri, int be, int en)
{
    if(le>en || ri<be) return n;
    else if(be<=le && ri<=en) return tree[v];
    else
    {
        int mid=(le+ri)/2;
        int p1=query(2*v, le, mid, be, en), p2=query(2*v+1, mid+1, ri, be, en);
        if(doseg[p1]<doseg[p2]) return p1;
        else return p2;
    }
}

struct event
{
    int be, en, nom;
    event() {}
    event(int a, int b, int c)
    {
        be=a;
        en=b;
        nom=c;
    }
};

bool operator<(event p, event q)
{
    return p.en<q.en;
}

int nnom[100005];
event ev[100005];
int par[20][100005];

void fill_table()
{
    for(int i=1; i<20; i++)
    {
        for(int j=0; j<n; j++) par[i][j]=par[i-1][par[i-1][j]];
    }
}

int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);

    cin>>n>>q;
    for(int i=0; i<n; i++)
    {
        cin>>ev[i].be>>ev[i].en;
        ev[i].nom=i+1;
    }
    sort(ev, ev+n);
    for(int i=0; i<n; i++) nnom[ev[i].nom]=i;
    doseg[n]=1e9;
    for(int i=0; i<n; i++)
    {
        int le=-1, ri=i;
        while(ri-le>1)
        {
            int mid=(le+ri)/2;
            if(ev[mid].en>=ev[i].be) ri=mid;
            else le=mid;
        }
        doseg[i]=ri;
        update(1, 0, n-1, i);
        par[0][i]=query(1, 0, n-1, doseg[i], i);
    }
    fill_table();
    for(int i=0; i<q; i++)
    {
        int le, ri;
        cin>>le>>ri;
        le=nnom[le];
        ri=nnom[ri];
        if(le==ri) cout<<0<<endl;
        else if(ev[le].en==ev[ri].en) cout<<1<<endl;
        else if(le>ri) cout<<"impossible\n";
        else if(doseg[par[19][ri]]>le) cout<<"impossible\n";
        else if(doseg[ri]<=le) cout<<1<<endl;
        else
        {
            int brpr=0;
            for(int i=19; i>=0; i--)
            {
                int p2=par[i][ri];
                if(doseg[p2]>le)
                {
                    brpr+=(1<<i);
                    ri=p2;
                }
            }
            cout<<brpr+2<<endl;
        }
    }
    return 0;
}

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