Submission #649742

#	Time	Username	Problem	Language	Result	Execution time	Memory
649742		ToroTN	Event Hopping (BOI22_events)	C++14	100 / 100	138 ms	19192 KiB

events

#include<bits/stdc++.h>
using namespace std;
#define pb push_back
#define X first
#define Y second
pair<int,int> seg[400005];
int n,t,s[100005],e[100005],l,r,x,y,idx[100005],it,p[100005][25],num,ex[100005],ans;
vector<tuple<int,int,int> > v;
void build(int tree,int st,int ed)
{
    int md=(st+ed)/2;
    if(st==ed)
    {
        seg[tree]={get<1>(v[st]),st};
        return;
    }
    build(2*tree,st,md);
    build(2*tree+1,md+1,ed);
    seg[tree]=max(seg[2*tree],seg[2*tree+1]);
}
pair<int,int> query(int tree,int st,int ed,int l,int r)
{
    int md=(st+ed)/2;
    if(st>r||ed<l)
    {
        return {(int)-2e9,(int)-2e9};
    }
    if(st>=l&&ed<=r)return seg[tree];
    return max(query(2*tree,st,md,l,r),query(2*tree+1,md+1,ed,l,r));
}
int main()
{
    scanf("%d%d",&n,&t);
    for(int i=1;i<=n;i++)
    {
        scanf("%d%d",&s[i],&e[i]);
        v.pb({-e[i],-s[i],i});
    }
    v.pb({-2e9,-2e9,-2e9});
    sort(v.begin(),v.end());
    for(int i=1;i<=n;i++)
    {
        idx[get<2>(v[i])]=i;
        l=get<0>(v[i]);
        r=get<1>(v[i]);
        //printf("%d %d %d\n",l,r,i);
    }
    build(1,1,n);
    for(int i=1;i<=n;i++)
    {
        it=lower_bound(v.begin(),v.end(),make_tuple(get<1>(v[i])+1,-2e9,-2e9))-v.begin()-1;
        num=query(1,1,n,i+1,it).Y;
        ex[i]=it;
        p[i][0]=num;
        //printf("itnum=%d %d\n",it,num);
    }
    for(int i=1;i<=n;i++)
    {
        if(p[i][0]<1||p[i][0]>n)p[i][0]=i;
    }
    for(int i=1;i<=20;i++)
    {
        for(int j=1;j<=n;j++)
        {
            p[j][i]=p[p[j][i-1]][i-1];
        }
    }
    while(t--)
    {
        scanf("%d%d",&x,&y);
        if(x==y)
        {
            printf("0\n");
            continue;
        }
        if(e[x]>e[y])
        {
            printf("impossible\n");
            continue;
        }
        x=idx[x];
        y=idx[y];
        ans=0;
        //printf("y=%d x=%d\n",y,x);
        for(int i=20;i>=0;i--)
        {
            //printf("%d\n",p[y][i]);
            if(p[y][i]<x&&ex[p[y][i]]<x)
            {
                if(y!=p[y][i])
                {
                    y=p[y][i];
                    ans+=(1<<i);
                }
                /*y=p[y][i];
                ans+=(1<<i);*/
            }
            //printf("%d %d\n",i,y);
        }
        if(x<=ex[y])
        {
            printf("%d\n",ans+1);
        }else if(x<=ex[p[y][0]])
        {
            printf("%d\n",ans+2);
        }else
        {
            printf("impossible\n");

        }
    }
}

Compilation message (stderr)

events.cpp: In function 'int main()':
events.cpp:33:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   33 |     scanf("%d%d",&n,&t);
      |     ~~~~~^~~~~~~~~~~~~~
events.cpp:36:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   36 |         scanf("%d%d",&s[i],&e[i]);
      |         ~~~~~^~~~~~~~~~~~~~~~~~~~
events.cpp:70:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   70 |         scanf("%d%d",&x,&y);
      |         ~~~~~^~~~~~~~~~~~~~

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