线段树之二

//poj 3667 Hotel

#include<iostream>            //线段树，求连续区间的长度
using namespace std;
struct node
{
    int l,r,blank;
    int lb,rb;        //lb(rb)记录从左(右)端点开始的连续空的线段长
}tree[2000000];
void build_tree(int n,int s,int t)
{
    tree[n].l=s;tree[n].r=t;
    tree[n].blank=tree[n].lb=tree[n].rb=t-s+1;
    if(s<t)
    {
        int mid=(s+t)>>1;
        build_tree(2*n,s,mid);
        build_tree(2*n+1,mid+1,t);
    }
}
void upd_blank(int n)    //在modify_in,modify_out,query函数内都要用到upd_blank,update来更新区间情况，所以封装起来
{
    if(tree[n].blank==0)
    {
        tree[2*n].blank=tree[2*n+1].blank=0;
        tree[2*n].lb=tree[2*n].rb=tree[2*n+1].lb=tree[2*n+1].rb=0;
    }
    if(tree[n].blank==tree[n].r-tree[n].l+1)
    {
        tree[2*n].blank=tree[2*n].r-tree[2*n].l+1;
        tree[2*n+1].blank=tree[2*n+1].r-tree[2*n+1].l+1;    
        tree[2*n].lb=tree[2*n].rb=tree[2*n].r-tree[2*n].l+1;
        tree[2*n+1].lb=tree[2*n+1].rb=tree[2*n+1].r-tree[2*n+1].l+1;    
    }
}
void update(int n)
{
    tree[n].blank=tree[2*n].blank+tree[2*n+1].blank;
    tree[n].lb=tree[2*n].lb;
    if(tree[2*n].lb==tree[2*n].r-tree[2*n].l+1)
        tree[n].lb+=tree[2*n+1].lb;
    tree[n].rb=tree[2*n+1].rb;
    if(tree[2*n+1].rb==tree[2*n+1].r-tree[2*n+1].l+1)
        tree[n].rb+=tree[2*n].rb;
}
void modify_in(int n,int s,int t)
{
    upd_blank(n);
    if(tree[n].l==s&&tree[n].r==t)    //这道题同样地不能一直更新到叶子节点，即tree[n].l==tree[n].r,否则TLE
    {
        tree[n].blank=0;
        tree[n].lb=tree[n].rb=0;
    }
    else
    {
        int mid=(tree[n].l+tree[n].r)>>1;
        if(s<=mid)
            modify_in(2*n,s,min(mid,t));
        if(t>mid)
            modify_in(2*n+1,max(s,mid+1),t);
        update(n);
    }
}
void modify_out(int n,int s,int t)
{
    upd_blank(n);
    if(tree[n].l==s&&tree[n].r==t)
    {    
        tree[n].blank=tree[n].lb=tree[n].rb=tree[n].r-tree[n].l+1;
    }
    else
    {
        int mid=(tree[n].l+tree[n].r)>>1;
        if(s<=mid)
            modify_out(2*n,s,min(mid,t));
        if(t>mid)
            modify_out(2*n+1,max(s,mid+1),t);
        update(n);
    }
}
bool query(int n,int len)
{
    upd_blank(n);
    if(tree[n].r-tree[n].l+1<len||tree[n].blank<len)
        return false;
    if(tree[n].blank==tree[n].r-tree[n].l+1)    
    {
        modify_in(n,tree[n].l,tree[n].l+len-1);       //假如是整个区间都为空的话自然地从左端开始
        update(n);
        printf("%d\n",tree[n].l);
        return true;
    }
//查询最左连续区间时，注意顺序，首先是左子树，然后是跨越左子树和右子树，即原来区间的中间部分，
//然后是右子树，最后如果都不满足的话则输出０
    if(tree[n].lb>=len)        
    {
        modify_in(n,tree[n].l,tree[n].l+len-1);
        update(n);
        printf("%d\n",tree[n].l);
        return true;
    }    
    if(query(2*n,len))
    {
        update(n);
        return true;
    }
    if(tree[2*n].rb+tree[2*n+1].lb>=len)
    {
        int a=tree[2*n].rb;        
//要特别注意这里必须用另一变量存储tree[2*n].rb,因为执行后面第一句modify_in()后，
//tree[2*n].rb的值将会发生改变，影响到接下来的正确执行
        modify_in(2*n,tree[2*n].r-a+1,tree[2*n].r);
        modify_in(2*n+1,tree[2*n+1].l,tree[2*n+1].l+len-a-1);
        update(n);
        printf("%d\n",tree[2*n].r-a+1);
        return true;
    }
    if(query(2*n+1,len))
    {
        update(n);
        return true;
    }
    return false;
}
int main()
{
    int n,m,tag,x,d;
    scanf("%d%d",&n,&m);
    build_tree(1,1,n);
    while(m--)
    {
        scanf("%d",&tag);
        if(tag==1)
        {
            scanf("%d",&d);            
            bool flag=query(1,d);
            if(!flag)
                printf("0\n");
        }
        else
        {
            scanf("%d%d",&x,&d);
            modify_out(1,x,x+d-1);    
        }
    }
    return 0;
}