线段树 习惯

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
#include<cstring>
#include<set>

using namespace std;

struct node1
{
    int x,y;
    int pos,f;
    friend bool operator <(node1 a,node1 b)
    {
        return a.pos<b.pos;
    }

}p[5005];

bool cmp(node1 a,node1 b)
{
    return a.pos<b.pos;
}


struct node
{
    int l,r;
    long long maxn;

    //long long v;
    int f;

} tree[50005*5];

node up(node cur, node x,node y)
{
    node ntree;

    ntree.maxn=max(x.maxn,y.maxn);
    ntree.l=x.l;
    ntree.r=y.r;
    ntree.f=cur.f;

    return ntree;
}

void down(int i)
{
    if(tree[i].f!=0)
    {
        tree[i*2].f+=tree[i].f;
        tree[i*2+1].f+=tree[i].f;

        tree[i*2].maxn+=tree[i].f;
        tree[i*2+1].maxn+=tree[i].f;

        tree[i].f=0;
    }
    return ;
}
void build(int i,int l,int r)
{
    tree[i].l=l;
    tree[i].r=r;
    tree[i].f=0;
    tree[i].maxn=0;
    if(l==r)
    {
        //tree[i].v=0;
        tree[i].maxn=0;

        return ;
    }
    else
    {
        int mid=(l+r)/2;
        build(i*2,l,mid);
        build(i*2+1,mid+1,r);

        tree[i]=up(tree[i],tree[i*2],tree[2*i+1]);
    }
}
void updata(int i,int l,int r,long long v)
{
    if(tree[i].l==l&&tree[i].r==r)
    {
        tree[i].maxn=v;
        return ;
    }
    int mid=(tree[i].l+tree[i].r)/2;

    down(i);
    if(r<=mid)
    {
        updata(i*2,l,r,v);
    }
    else if(l>mid)
        updata(i*2+1,l,r,v);
    else
    {
        updata(i*2,l,mid,v);
        updata(i*2+1,mid+1,r,v);
    }

    tree[i]=up(tree[i],tree[i*2],tree[2*i+1]);
}

void updata1(int i,int l,int r,long long v)
{
    if(tree[i].l==l&&tree[i].r==r)
    {
        tree[i].maxn+=v;
        tree[i].f+=v;
        return ;
    }
    int mid=(tree[i].l+tree[i].r)/2;

    down(i);
    if(r<=mid)
    {
        updata1(i*2,l,r,v);
    }
    else if(l>mid)
        updata1(i*2+1,l,r,v);
    else
    {
        updata1(i*2,l,mid,v);
        updata1(i*2+1,mid+1,r,v);
    }

    tree[i]=up(tree[i],tree[i*2],tree[2*i+1]);
}


node get(int i,int l,int r)
{

    if(tree[i].l==l&&tree[i].r==r)
    {
        return tree[i];
    }

    down(i);
    int mid=(tree[i].l+tree[i].r)/2;

    if(r<=mid)
        return get(i*2,l,r);
    else if(l>mid)
        return get(i*2+1,l,r);
    else
    {
        node c;
        node a=get(i*2,l,mid);
        node b=get(i*2+1,mid+1,r);
        return up(c,a,b);
    }

}

int s[2005];

int main()
{
    int t;
    scanf("%d",&t);
    int cas=0;
    while(t--)
    {
        cas++;
        int n;
        scanf("%d",&n);
        int cnt=0;
        for(int i=0;i<n;i++)
        {
            int x,y;
            scanf("%d%d",&x,&y);
            y++;

            p[cnt].x=x;
            p[cnt].y=y;
            p[cnt].pos=x;
            p[cnt].f=1;
            cnt++;

            p[cnt].x=x;
            p[cnt].y=y;
            p[cnt].pos=y;
            p[cnt].f=-1;
            cnt++;

        }

        sort(p,p+cnt,cmp);
        int ans=0;

        int curc=0;

        build(1,1,cnt);
        for(int i=0;i<cnt;i++)
        {
            if(p[i].f==1)
            {
                curc++;
                int maxn;
                if(i!=0)
                    maxn=get(1,1,i).maxn;
                else
                    maxn=0;

                updata(1,i+1,i+1,maxn);

                if(curc>=3)
                   ans=max(ans,maxn+curc);

                s[i]=curc;

            }
            else
            {
                curc--;
                int pre=p[i].x;

                node1 tp;
                tp.pos=pre;

                int preid=lower_bound(p,p+cnt,tp)-p;
                //cout<<preid<<endl;
                updata1(1,preid+1,i,1);
                int maxn=get(1,1,i).maxn;
                updata(1,i+1,i+1,maxn);

                if(curc>=3)
                ans=max(ans,maxn+curc);

                 s[i]=curc;

            }
        }

        printf("Case #%d: ",cas);
        printf("%d\n",ans);



    }
}