HDU 4251 The Famous ICPC Team Again

这个也是一道对划分树的简单的运用：

#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<algorithm>
#include<cmath>
#include<queue>
#include<set>
#include<map>
#include<cstring>
#include<vector>
using namespace std;
class Node
{
public:
      int num[100024],val[100024];    
}node[20];
int val[100024];
bool cmp( int a , int b )
{
     return a <= b;
}
void build_tree( int l , int r , int deep )
{
     if( l == r ) return ;
     int mid = ( l + r )>>1;
     int issame = mid - l + 1 ,same = 0;
     for( int i = l ; i <= r ; i ++ )
          if( node[deep].val[i] < val[mid] ) issame --;
    int left = l ,right = mid + 1;
    for( int i = l ; i <= r ; i ++ )
    {
          node[deep].num[i] = node[deep].num[i-1];
          if( node[deep].val[i] > val[mid] )
              node[deep+1].val[right++] = node[deep].val[i];
          else if( node[deep].val[i] < val[mid] )
          {
               node[deep+1].val[left++] = node[deep].val[i];
               node[deep].num[i] ++;
          }
          else
          {
              if( same < issame )
              {
                  same ++;
                  node[deep+1].val[left++] = node[deep].val[i];
                  node[deep].num[i] ++;        
              }    
              else     node[deep+1].val[right++] = node[deep].val[i];
          }            
    }
    build_tree( l , mid , deep + 1 );
    build_tree( mid + 1, r ,deep + 1 ); 
}
int find( int a , int b , int k ,int deep, int l ,int r )
{
    //printf( "l=%d,r=%d,s=%d,t=%d,k=%d,dep=%d\n",l,r,a,b,k,deep);system("pause");
     int mid = ( l + r )>>1;
     if( a == b ) return node[deep].val[a];
     int d = node[deep].num[b] - node[deep].num[a-1];
     int s = node[deep].num[a-1] - node[deep].num[l-1];
     int ss = node[deep].num[b] - node[deep].num[l-1];
     int rx =  a - l  + 1 - s,ry = b - l + 1 - ss;
     if( d >= k )  return find( l + s , l + ss - 1 ,k , deep + 1, l , mid );
     else return find( mid + rx , mid + ry , k - d , deep + 1 , mid + 1 , r );
}
int main(  )
{
    int n,m,Case=1,l,r;
    while( scanf( "%d",&n )==1 )
    {
        for( int i = 1 ; i <= n ; i ++ )
        {
            scanf( "%d",&node[0].val[i] );
            val[i] = node[0].val[i];    
        }    
        sort( val+1, val + n + 1, cmp );
        build_tree( 1 , n  , 0 ); 
//        printf( "sfaf" );
        scanf( "%d",&m );
        printf( "Case %d:\n",Case++ );
        for( int i = 0 ; i < m ; i ++ )
        {
             scanf( "%d %d",&l,&r );
             int k = ( r - l )/2 + 1 ;
             printf( "%d\n",find( l  , r , k, 0 , 1, n  ) );    
        }
    }
    //system( "pause" );
    return 0;
}