Submission #721067

#	Time	Username	Problem	Language	Result	Execution time	Memory
721067		Rafi22	Event Hopping (BOI22_events)	C++14	100 / 100	459 ms	49528 KiB

events

#include <bits/stdc++.h>

using namespace std;

#define int long long
#define endl '\n'
#define st first
#define nd second
#define pb push_back
#define sz(x) (int)(x).size()
#define all(x) (x).begin(), (x).end()
#define ll long long
ll mod=1000000007;
int inf=1000000007;
ll infl=1000000000000000007;

const int N=100007,L=17,pot=1<<18;

int l[N],r[N];
int skok[N][L];
map<int,int>M;

pair<int,int>seg[2*pot+7];

void ins(int v,int x,int i)
{
    v+=pot-1;
    seg[v]=min(seg[v],{x,i});
    while(v>1)
    {
        v/=2;
        seg[v]=min(seg[2*v],seg[2*v+1]);
    }
}
pair<int,int>que(int v,int a,int b,int l,int r)
{
    if(a<=l&&b>=r) return seg[v];
    if(r<a||l>b) return {inf,0};
    return min(que(2*v,a,b,l,(l+r)/2),que(2*v+1,a,b,(l+r)/2+1,r));
}

signed main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int n,q;
    cin>>n>>q;
    set<int>S;
    for(int i=1;i<=n;i++)
    {
        cin>>l[i]>>r[i];
        S.insert(l[i]);
        S.insert(r[i]);
    }
    int it=0;
    for(auto x:S) M[x]=++it;
    for(int i=1;i<=n;i++)
    {
        l[i]=M[l[i]];
        r[i]=M[r[i]];
    }
    for(int i=1;i<2*pot;i++) seg[i].st=inf;
    for(int i=1;i<=n;i++) ins(r[i],l[i],i);
    for(int i=1;i<=n;i++) skok[i][0]=que(1,l[i],r[i],1,pot).nd;
    for(int j=1;j<L;j++) for(int i=1;i<=n;i++) skok[i][j]=skok[skok[i][j-1]][j-1];
    while(q--)
    {
        int a,b;
        cin>>a>>b;
        int ans=0;
        for(int i=L-1;i>=0;i--)
        {
            if(l[skok[b][i]]>r[a])
            {
                ans+=(1<<i);
                b=skok[b][i];
            }
        }
        if(a==b) cout<<0<<endl;
        else if(r[b]<r[a]) cout<<"impossible"<<endl;
        else if(l[b]<=r[a]) cout<<1<<endl;
        else if(l[skok[b][0]]<=r[a]) cout<<ans+2<<endl;
        else cout<<"impossible"<<endl;
    }

    return 0;
}

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