POJ 3667 Hotel

POJ 3667 Hotel

经典的区间合并题。
参考这篇文章学习的， http://www.notonlysuccess.com/?p=978
以下是我的代码：

/*
 * Author:  lee1r
 * Created Time:  2011/8/4 18:38:40
 * File Name: poj3667.cpp
  */
#include < iostream >
#include < sstream >
#include < fstream >
#include < vector >
#include < list >
#include < deque >
#include < queue >
#include < stack >
#include < map >
#include < set >
#include < bitset >
#include < algorithm >
#include < cstdio >
#include < cstdlib >
#include < cstring >
#include < cctype >
#include < cmath >
#include < ctime >
#define  L(x) ((x)<<1)
#define  R(x) ((x)<<1|1)
#define  Half(x) ((x)>>1)
#define  lowbit(x) ((x)&(-(x)))
using   namespace  std;
const   int  kInf( 0x7f7f7f7f );
const   double  kEps(1e - 11 );
typedef  long   long  int64;
typedef unsigned  long   long  uint64;

const   int  kMaxn( 50007 );

struct  Node
{
     int  a,b;
     int  max,lmax,rmax;
     bool  cover;
};

int  n,m;
Node tree[kMaxn << 2 ];

void  Build( int  node, int  x, int  y)
{
    tree[node].a = x;
    tree[node].b = y;
    tree[node].max = tree[node].lmax = tree[node].rmax = y - x + 1 ;
    tree[node].cover = false ;
     if (x < y)
    {
         int  m(Half(x + y));
        Build(L(node),x,m);
        Build(R(node),m + 1 ,y);
    }
}

void  PushDown( int  node)
{
     if ( ! tree[node].cover)
         return ;
    tree[node].cover = false ;
    tree[L(node)].cover = tree[R(node)].cover = true ;
     if (tree[node].max)
    {
        tree[L(node)].max = tree[L(node)].lmax = tree[L(node)].rmax = tree[L(node)].b - tree[L(node)].a + 1 ;
        tree[R(node)].max = tree[R(node)].lmax = tree[R(node)].rmax = tree[R(node)].b - tree[R(node)].a + 1 ;
    }
     else
    {
        tree[L(node)].max = tree[L(node)].lmax = tree[L(node)].rmax = 0 ;
        tree[R(node)].max = tree[R(node)].lmax = tree[R(node)].rmax = 0 ;
    }
}

void  PushUp( int  node)
{
    tree[node].max = max(tree[L(node)].max,tree[R(node)].max);
    tree[node].max = max(tree[node].max,tree[L(node)].rmax + tree[R(node)].lmax);
     if (tree[L(node)].max == tree[L(node)].b - tree[L(node)].a + 1 )
        tree[node].lmax = tree[L(node)].max + tree[R(node)].lmax;
     else
        tree[node].lmax = tree[L(node)].lmax;
     if (tree[R(node)].max == tree[R(node)].b - tree[R(node)].a + 1 )
        tree[node].rmax = tree[L(node)].rmax + tree[R(node)].max;
     else
        tree[node].rmax = tree[R(node)].rmax;
}

void  Modify( int  node, int  x, int  y, int  sign)
{
     int  len(tree[node].b - tree[node].a + 1 );
     if (x <= tree[node].a  &&  tree[node].b <= y)
    {
        tree[node].cover = true ;
         if (sign == 0 )
            tree[node].max = 0 ;
         else
            tree[node].max = len;
        tree[node].lmax = tree[node].rmax = tree[node].max;
         return ;
    }
    PushDown(node);
     int  m(Half(tree[node].a + tree[node].b));
     if (m >= x)
        Modify(L(node),x,y,sign);
     if (m < y)
        Modify(R(node),x,y,sign);
    PushUp(node);
}

int  Query( int  node, int  need)
{
     if (tree[node].max < need)
         return   0 ;
     if (tree[node].a == tree[node].b)
         return  tree[node].a;
    PushDown(node);
     if (tree[node].lmax >= need)
         return  tree[node].a;
     if (tree[L(node)].max >= need)
         return  Query(L(node),need);
     if (tree[L(node)].rmax + tree[R(node)].lmax >= need)
         return  tree[L(node)].b - tree[L(node)].rmax + 1 ;
     return  Query(R(node),need);
}

int  main()
{
     // freopen("data.in","r",stdin);
    
     while (scanf( " %d%d " , & n, & m) == 2 )
    {
        Build( 1 , 1 ,n);
        
         while (m -- )
        {
             int  cmd;
            scanf( " %d " , & cmd);
             if (cmd == 1 )
            {
                 int  a,result;
                scanf( " %d " , & a);
                result = Query( 1 ,a);
                printf( " %d\n " ,result);
                 if (result)
                    Modify( 1 ,result,result + a - 1 , 0 );
            }
             else
            {
                 int  a,b;
                scanf( " %d%d " , & a, & b);
                Modify( 1 ,a,a + b - 1 , 1 );
            }
        }
    }
    
     return   0 ;
}