hdu1856

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      #include
    
      <
    
      iostream
    
      >
    
      

    
      using
    
       
    
      namespace
    
       std;

    
      #define
    
       M 10000001
    
      

    
      int
    
       father[M];

    
      int
    
       _max;

    
      int
    
       sum[M];

    
      int
    
       FindFa( 
    
      int
    
       a )
{

    
      if
    
      ( father[a] 
    
      ==
    
       a )
{

    
      return
    
       a;
}

    
      return
    
       father[a] 
    
      =
    
       FindFa( father[a] ); }

    
      void
    
       UnionFa( 
    
      int
    
       a , 
    
      int
    
       b ) 
    
      //
    
      将a,b合并
    
      

    
      {
father[b] 
    
      =
    
       a; 
    
      //
    
      把a设为b的父结点
    
      

    
      sum[a] 
    
      +=
    
       sum[b]; 
    
      //
    
      当有元素加入a中时，使其个数加sum[b]个
    
      

    
      if
    
      ( sum[a] 
    
      >
    
       _max )
{ _max 
    
      =
    
       sum[a]; }
}

    
      int
    
       main()
{

    
      int
    
       a , b , n;

    
      int
    
       i;

    
      while
    
      ( scanf( 
    
      "
    
      %d
    
      "
    
       , 
    
      &
    
      n ) 
    
      !=
    
       EOF ) 
{
_max 
    
      =
    
       
    
      1
    
      ;

    
      for
    
      ( i 
    
      =
    
       
    
      0
    
       ; i 
    
      <
    
       M ; 
    
      ++
    
      i )
{ father[i] 
    
      =
    
       i; sum[i] 
    
      =
    
       
    
      1
    
      ; }

    
      for
    
      ( i 
    
      =
    
       
    
      0
    
       ; i 
    
      <
    
       n ; 
    
      ++
    
      i )
{
scanf( 
    
      "
    
      %d %d
    
      "
    
       , 
    
      &
    
      a , 
    
      &
    
      b );
a 
    
      =
    
       FindFa( a );
b 
    
      =
    
       FindFa( b );


    
      if
    
      ( a 
    
      !=
    
       b )
{ UnionFa( a , b ); } 
}
printf( 
    
      "
    
      %d\n
    
      "
    
       , _max );
}

    
      return
    
       
    
      0
    
      ;
}

 
   
     

http://acm.hdu.edu.cn/showproblem.php?pid=1856