POJ 2352 Stars (树状数组)

题意：给定一组点，问二维空间中各个点的等级是多少，点的等级定义如下：其左下方点的个数。

思路：昨天看了树状数组，然后怀着无比激动的心情开始了，一阵子思考--不会，在一阵子思考--还是不会，只能硬着头皮翻报告......终于明白树状数组是怎么应用了....汗了....到现在才开始学树状数组....不管怎么说，树状数组的确是一个强大的在线数据结构！

  
    

   
     
   
     #include 
   
     <
   
     iostream
   
     >
   
     
#include 
   
     <
   
     cstdio
   
     >
   
     
#include 
   
     <
   
     algorithm
   
     >
   
     
#include 
   
     <
   
     memory.h
   
     >
   
     
#include 
   
     <
   
     cmath
   
     >
   
     
#include 
   
     <
   
     ctime
   
     >
   
     
#include 
   
     <
   
     bitset
   
     >
   
     
#include 
   
     <
   
     queue
   
     >
   
     
#include 
   
     <
   
     vector
   
     >
   
     

   
     using
   
      
   
     namespace
   
      std;


   
     const
   
      
   
     int
   
      BORDER 
   
     =
   
      (
   
     1
   
     <<
   
     20
   
     )
   
     -
   
     1
   
     ;

   
     const
   
      
   
     int
   
      MAXSIZE 
   
     =
   
      
   
     37
   
     ;

   
     const
   
      
   
     int
   
      MAXN 
   
     =
   
      
   
     40000
   
     ;

   
     const
   
      
   
     int
   
      INF 
   
     =
   
      
   
     1000000000
   
     ;

   
     #define
   
      CLR(x,y) memset(x,y,sizeof(x))
   
     

   
     #define
   
      ADD(x) x=((x+1)&BORDER)
   
     

   
     #define
   
      IN(x) scanf("%d",&x)
   
     

   
     #define
   
      OUT(x) printf("%d\n",x)
   
     

   
     #define
   
      MIN(m,v) (m)<(v)?(m):(v)
   
     

   
     #define
   
      MAX(m,v) (m)>(v)?(m):(v)
   
     

   
     #define
   
      ABS(x) ((x)>0?(x):-(x))
   
     


   
     int
   
      tre[MAXN],ans[MAXN],arr[MAXN];

   
     int
   
      n_tre,n;


   
     int
   
      init()
{
 CLR(tre,
   
     0
   
     );
 CLR(ans,
   
     0
   
     );
 CLR(arr,
   
     0
   
     );
 n_tre 
   
     =
   
      MAXN;
 
   
     return
   
      
   
     0
   
     ;
}

   
     int
   
      lowbit(
   
     int
   
      x)
{
 
   
     return
   
      x
   
     &
   
     (
   
     -
   
     x);
}

   
     void
   
      modify(
   
     int
   
      ind,
   
     int
   
      delta)
{
 
   
     while
   
     ( ind 
   
     <=
   
      n_tre)
 {
 tre[ind] 
   
     +=
   
      delta;
 ind 
   
     +=
   
      lowbit(ind);
 }
}

   
     int
   
      get_sum(
   
     int
   
      ind)
{
 
   
     int
   
      sum 
   
     =
   
      
   
     0
   
     ;
 
   
     while
   
     (ind 
   
     !=
   
      
   
     0
   
     )
 {
 sum 
   
     +=
   
      tre[ind];
 ind 
   
     -=
   
      lowbit(ind);
 }
 
   
     return
   
      sum;
}

   
     int
   
      work()
{
 
   
     int
   
      i,b,a,j,tmp;
 
   
     for
   
     (i 
   
     =
   
      
   
     0
   
     ; i 
   
     <
   
      n; 
   
     ++
   
     i)
 {
 scanf(
   
     "
   
     %d%d
   
     "
   
     ,
   
     &
   
     a,
   
     &
   
     b);
 
   
     ++
   
     a;
 
   
     ++
   
     ans[get_sum(a)];
 modify(a,
   
     1
   
     );
 }
 
   
     for
   
     (i 
   
     =
   
      
   
     0
   
     ; i 
   
     <
   
      n; 
   
     ++
   
     i)
 OUT(ans[i]);
 
   
     return
   
      
   
     0
   
     ;
}

   
     int
   
      main()
{
 
   
     while
   
     (IN(n)
   
     !=
   
     EOF)
 {
 init();
 work();
 }
 
   
     return
   
      
   
     0
   
     ;
}