HDU 1754 I Hate It

HDU 1754 I Hate It

更新区间中的点，维护区间最大值。
以下是我的代码：

#include < stdio.h >
const   long  maxn = 200007 ,maxm = 5007 ;
typedef  struct
{
     long  a,b,max;
     long  left,right;
}node;
long  n,m,tot,rp[maxn];
node tree[maxn * 7 ];
long  max( long  a, long  b)
{
     return  (a > b ? a:b);
}
void  build( long  x, long  y)
{
     long  now =++ tot,mid = (x + y) >> 1 ;
    tree[now].a = x;tree[now].b = y;
     if (x == y)
      tree[now].max = rp[x];
     else   if (x < y)
    {
       tree[now].left = tot + 1 ;build(x,mid);
       tree[now].right = tot + 1 ;build(mid + 1 ,y);
       tree[now].max = max(tree[tree[now].left].max,tree[tree[now].right].max);
    }
}
void  insert( long  id, long  node)
{
     long  a = tree[node].a,b = tree[node].b,mid = (a + b) >> 1 ;
     if (id == a && id == b)
      tree[node].max = max(tree[node].max,rp[id]);
     else
    {
        if (id <= mid)
         insert(id,tree[node].left);
        else
         insert(id,tree[node].right);
       tree[node].max = max(tree[tree[node].left].max,tree[tree[node].right].max);
    }
}
long  getmax( long  x, long  y, long  node)
{
     long  a = tree[node].a,b = tree[node].b,mid = (a + b) >> 1 ,re =- 1 ;
     if (x <= a && b <= y)
       return  tree[node].max;
     if (mid >= x)
      re = max(re,getmax(x,y,tree[node].left));
     if (mid + 1 <= y)
      re = max(re,getmax(x,y,tree[node].right));
     return  re;
}
int  main()
{
     /*
    freopen("data.in","r",stdin);
    freopen("data.out","w",stdout);
    // */
     while (scanf( " %ld%ld " , & n, & m) == 2 )
    {
        for ( long  i = 1 ;i <= n;i ++ ) scanf( " %ld " , & rp[i]);getchar();
       tot = 0 ;
       build( 1 ,n);
        //   Build A Segment Tree
        for ( long  i = 1 ;i <= m;i ++ )
       {
           char  cmd;
           long  a,b;
           // for(long i=1;i<=tot;i++)printf("[%ld,%ld]'max is %ld\n",tree[i].a,tree[i].b,tree[i].max);
          cmd = getchar();
          scanf( " %ld%ld " , & a, & b);getchar();
           switch (cmd)
          {
              case   ' Q ' :
                 if (a > b)
                {
                    long  t = a;a = b;b = t;
                }
                printf( " %ld\n " ,getmax(a,b, 1 ));
                 break ;
              case   ' U ' :
                rp[a] = b;
                insert(a, 1 );
          }
       }
    }
return   0 ;
}