Submission #1077142

#	Time	Username	Problem	Language	Result	Execution time	Memory
1077142		LIF	Event Hopping (BOI22_events)	C++14	10 / 100	1580 ms	66352 KiB

events

#include<bits/stdc++.h>
using namespace std;
int n,q,l[500005],r[500005];
int su[800005];
int dis[5005][5005];
struct nod
{
    int ll;
    int rr;
    int id;
}node[500005];
bool cmp(nod x,nod y)
{
   if(x.rr == y.rr)return x.ll < y.ll;
   else return x.rr < y.rr;
}
void pushup(int rt)
{
    su[rt] = min(su[rt<<1],su[rt<<1|1]);
    return;
}
void build(int l,int r,int rt,int now)
{
    if(l == r)
    {
        su[rt] = dis[now][l];
        return;
    }
    int mid = (l+r)>>1;
    build(l,mid,rt<<1,now);
    build(mid+1,r,rt<<1|1,now);
    pushup(rt);
    return;
}
int query(int l,int r,int queryl,int queryr,int rt)
{
    if(queryl <= l && r <= queryr)
    {
        return su[rt];
    }
    int maxn = 1e9+2e6;
    int mid = (l+r)>>1;
    if(mid >= queryl)maxn = min(maxn,query(l,mid,queryl,queryr,rt<<1));
    if(mid+1 <= queryr)maxn = min(maxn,query(mid+1,r,queryl,queryr,rt<<1|1));
    return maxn;
}
void change(int l,int r,int askl,int askr,int val,int rt)
{
    if(askl <= l && r <= askr)
    {
        su[rt] = val;
        return;
    }
    int mid = (l+r)>>1;
    if(mid >= askl)change(l,mid,askl,askr,val,rt<<1);
    if(mid+1 <= askr)change(mid+1,r,askl,askr,val,rt<<1|1);
    pushup(rt);
    return;
}
int main()
{
    //freopen("std.out","wb",stdout);
    cin>>n>>q;
    for(int i=1;i<=n;i++)
    {
        scanf("%d%d",&l[i],&r[i]);
        nod temp = nod{l[i],r[i],i};
        node[i] = temp;
    }
    sort(node+1,node+n+1,cmp);
    for(int now = 1;now<=n;now++)
    {
            for(int i=1;i<=n;i++)dis[now][i] = 1e9;
            int init,target;
            init = now;
            int num = 0;
            for(int i=1;i<=n;i++)
            {
                if(node[i].ll == l[init] && node[i].rr == r[init])
                {
                    num = i;
                    break;
                }
            }
            dis[now][node[num].id] = 0;
            build(1,n,1,now);
            change(1,n,num,num,dis[now][node[num].id],1);
            for(int i=num+1;i<=n;i++)
            {
                int l = 1;
                int r = i-1;
                int ans = -1;
                while(l <= r)
                {
                    int mid = (l+r)>>1;
                    if(node[mid].rr >= node[i].ll)
                    {
                        ans = mid;
                        r = mid - 1;
                    }
                    else l = mid + 1;
                }

                //即[ans,i-1]是滿足rr >= ll的;
                
                //cout<<"yeah2"<<endl;
                if(ans != -1)dis[now][node[i].id] = query(1,n,ans,i-1,1) + 1;
                //cout<<"yeah3"<<endl;
                change(1,n,i,i,dis[now][node[i].id],1);
                //cout<<"yeah4"<<endl;
            }  
        }  
    while(q--)
    {
        int x,y;
        cin>>x>>y;
        if(dis[x][y] >= 1e9)
        {
            cout<<"impossible"<<endl;
        }
        else cout<<dis[x][y]<<endl;
    }

        return 0;
}

Compilation message (stderr)

events.cpp: In function 'int main()':
events.cpp:74:22: warning: unused variable 'target' [-Wunused-variable]
   74 |             int init,target;
      |                      ^~~~~~
events.cpp:66:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   66 |         scanf("%d%d",&l[i],&r[i]);
      |         ~~~~~^~~~~~~~~~~~~~~~~~~~

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