HDU 4251 The Famous ICPC Team Again

这个也是一道对划分树的简单的运用：

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#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;

}