HDU 1166 敌兵布阵

HDU 1166 敌兵布阵

此题是第三次AC了。第一次高二的时候刚开始学线段树，然后前端时间复习线段树，然后就是这次用树状数组实现。
以下是我的代码：

#include < iostream >
#include < string >
#include < cstdio >
#include < cstring >
#define  lowbit(x) ((x)&(-(x)))  //  2^k
using   namespace  std;
const   int  kMaxn( 50007 );

int  n,bit[kMaxn];

void  Add( int  pos, int  delta)
{
     while (pos <= n)
    {
        bit[pos] += delta;
        pos += lowbit(pos);
    }
}

int  Sum( int  pos)
{
     int  re( 0 );
     while (pos > 0 )
    {
        re += bit[pos];
        pos -= lowbit(pos);
    }
     return  re;
}

int  main()
{
     int  T;
    scanf( " %d " , & T);
     for ( int  case_num = 1 ;case_num <= T;case_num ++ )
    {
        scanf( " %d " , & n);
        memset(bit, 0 , sizeof (bit));
         for ( int  i = 1 ;i <= n;i ++ )
        {
             int  t;
            scanf( " %d " , & t);
            Add(i,t);
        }
        printf( " Case %d:\n " ,case_num);
         string  cmd;
         while (cin >> cmd  &&  cmd != " End " )
        {
             if (cmd == " Add " )
            {
                 int  a,b;
                scanf( " %d%d " , & a, & b);
                Add(a,b);
            }
             else   if (cmd == " Sub " )
            {
                 int  a,b;
                scanf( " %d%d " , & a, & b);
                Add(a, - b);
            }
             else   if (cmd == " Query " )
            {
                 int  a,b;
                scanf( " %d%d " , & a, & b);
                printf( " %d\n " ,Sum(b) - Sum(a - 1 ));
            }
        }
    }

     return   0 ;
}