Submission #1167207

#	Time	Username	Problem	Language	Result	Execution time	Memory
1167207		son2008	Event Hopping (BOI22_events)	C++20	100 / 100	141 ms	24000 KiB

events

#include<bits/stdc++.h>
using namespace std;
#define task "task"
#define ii pair<int,int>
#define fi first
#define se second
//#define int long long
#define ll long long
#define ld double
#define mp make_pair
#define lg2 20
#define iii pair<int,ii>
#define iiii pair<ii,ii>
#define base 29
#define eps 1e-8
int dx[]= {0LL,0LL,1,-1,1,1,-1,-1};
int dy[]= {1,-1,0LL,0LL,1,-1,1,-1};
const int maxn=4e5+1;
const int mod=1e9+7;
int n,q,s[maxn],e[maxn],sz,P[maxn][lg2+1];
vector<int>nen;
ii tree[4*maxn];
void update(int i,ii val,int id=1,int l=1,int r=sz)
{
    if(l==r)
    {
        tree[id]=min(tree[id],val);
        return;
    }
    int mid=(l+r)/2;
    if(i<=mid)
    update(i,val,id*2,l,mid);
    else update(i,val,id*2+1,mid+1,r);
    tree[id]=min(tree[id*2],tree[id*2+1]);
}
ii get(int u,int v,int id=1,int l=1,int r=sz)
{
    if(u>r||v<l)return mp(1e9,1e9);
    if(u<=l&&v>=r)return tree[id];
    int mid=(l+r)/2;
    return min(get(u,v,id*2,l,mid),get(u,v,id*2+1,mid+1,r));
}
signed main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    if(fopen(task".inp","r"))
    {
        freopen(task".inp","r",stdin);
        freopen(task".out","w",stdout);
    }
    cin>>n>>q;
    for(int i=1;i<=n;i++)
    {
        cin>>s[i]>>e[i];
        nen.push_back(s[i]);
        nen.push_back(e[i]);
    }
    sort(nen.begin(),nen.end());
    nen.erase(unique(nen.begin(),nen.end()),nen.end());
    sz=nen.size();
    memset(tree,0x3f,sizeof(tree));
    for(int i=1;i<=n;i++)
    {
        int l=lower_bound(nen.begin(),nen.end(),s[i])-nen.begin()+1;
        int r=lower_bound(nen.begin(),nen.end(),e[i])-nen.begin()+1;
        update(r,mp(s[i],i));
    }
    for(int i=1;i<=n;i++)
    {
        int l=lower_bound(nen.begin(),nen.end(),s[i])-nen.begin()+1;
        int r=lower_bound(nen.begin(),nen.end(),e[i])-nen.begin()+1;
        P[i][0]=get(l,r).se;
    }
    for(int j=1;j<=lg2;j++)
    {
        for(int i=1;i<=n;i++)
        {
            P[i][j]=P[P[i][j-1]][j-1];
        }
    }
    while(q--)
    {
        int l,r;
        cin>>l>>r;
        if(l==r)
        {
            cout<<0<<'\n';
            continue;
        }
        if(e[l]>e[r])
        {
            cout<<"impossible"<<'\n';
            continue;
        }
        if(e[l]>=s[r])
        {
            cout<<1<<'\n';
            continue;
        }
        int ans=2;
        for(int i=lg2;i>=0;i--)
        {
            if(s[P[r][i]]>e[l])
            {
                ans+=(1<<i);
                r=P[r][i];
            }
        }
        r=P[r][0];
        if(s[r]>e[l])
        {
            cout<<"impossible"<<'\n';
            continue;
        }
        cout<<ans<<'\n';
    }
    cerr <<endl<< "TIME : " << clock() * 0.001 << "s" << endl ;
}

Compilation message (stderr)

events.cpp: In function 'int main()':
events.cpp:50:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   50 |         freopen(task".inp","r",stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
events.cpp:51:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   51 |         freopen(task".out","w",stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~

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