POJ 1655 Balancing Act (dfs)

题意：给定一棵树，问拿掉那个点，能使余下的各个子树结点个数上限最小。

看了半天，只知道是深搜，可是想了很久也没想出实现方法，各种菜~~~~看了大牛的实现，才恍然大悟........dfs的灵活之处自己需要时间去掌握啊.

 

  
    

   
     
   
     #include 
   
     <
   
     iostream
   
     >
   
     
#include 
   
     <
   
     cstdio
   
     >
   
     
#include 
   
     <
   
     algorithm
   
     >
   
     
#include 
   
     <
   
     memory.h
   
     >
   
     
#include 
   
     <
   
     cmath
   
     >
   
     
#include 
   
     <
   
     set
   
     >
   
     
#include 
   
     <
   
     queue
   
     >
   
     
#include 
   
     <
   
     vector
   
     >
   
     

   
     using
   
      
   
     namespace
   
      std;


   
     const
   
      
   
     int
   
      BORDER 
   
     =
   
      (
   
     1
   
     <<
   
     20
   
     )
   
     -
   
     1
   
     ;

   
     #define
   
      MAXN 20020
   
     

   
     #define
   
      INF 0x7ffffff
   
     

   
     #define
   
      CLR(x,y) memset(x,y,sizeof(x))
   
     

   
     #define
   
      ADD(x) ((++x)&BORDER)
   
     

   
     #define
   
      IN(x) scanf("%d",&x)
   
     

   
     #define
   
      OUT(x) printf("%d\n",x)
   
     

   
     #define
   
      MIN(m,v) (m)<(v)?(m):(v)
   
     

   
     #define
   
      MAX(m,v) (m)>(v)?(m):(v)
   
     

   
     #define
   
      ABS(x) (x>0?x:-x)
   
     


   
     struct
   
      EDGE{
 
   
     int
   
      v,next;
}edge[MAXN
   
     *
   
     2
   
     ];

   
     int
   
      n,m,cnt,mmin_index,mmin_cnt,index;

   
     int
   
      net[MAXN],visit[MAXN];

   
     void
   
      add_edge(
   
     const
   
      
   
     int
   
     &
   
      u,
   
     const
   
      
   
     int
   
     &
   
      v)
{
 edge[index].v 
   
     =
   
      v;
 edge[index].next 
   
     =
   
      net[u];
 net[u] 
   
     =
   
      index;
 
   
     ++
   
     index;
 edge[index].v 
   
     =
   
      u;
 edge[index].next 
   
     =
   
      net[v];
 net[v] 
   
     =
   
      index;
 
   
     ++
   
     index;
}

   
     int
   
      init()
{
 index 
   
     =
   
      
   
     0
   
     ;
 mmin_index 
   
     =
   
      INF;
 mmin_cnt 
   
     =
   
      INF;
 CLR(net,
   
     -
   
     1
   
     );
 CLR(visit,
   
     0
   
     );
 
   
     return
   
      
   
     0
   
     ;
}

   
     int
   
      dfs(
   
     const
   
      
   
     int
   
     &
   
      u)
{
 
   
     int
   
      i,v;
 
   
     int
   
      mmax 
   
     =
   
      
   
     0
   
     ;
 
   
     int
   
      sum 
   
     =
   
      
   
     0
   
     ;
 visit[u] 
   
     =
   
      
   
     1
   
     ;
 
   
     for
   
     (i 
   
     =
   
      net[u]; i 
   
     !=
   
      
   
     -
   
     1
   
     ; i 
   
     =
   
      edge[i].next)
 {
 v 
   
     =
   
      edge[i].v;
 
   
     if
   
     (
   
     !
   
     visit[v])
 {
 
   
     int
   
      tmp 
   
     =
   
      dfs(v);
 mmax 
   
     =
   
      MAX(mmax,tmp);
 sum 
   
     +=
   
      tmp;
 }
 }
 mmax 
   
     =
   
      MAX(mmax,n
   
     -
   
     sum
   
     -
   
     1
   
     );
 
   
     if
   
     (mmin_cnt 
   
     >=
   
      mmax)
 {
 
   
     if
   
     (mmin_cnt 
   
     ==
   
      mmax 
   
     &&
   
      mmin_index 
   
     <
   
      u)
 ;
 
   
     else
   
     
 {
 mmin_cnt 
   
     =
   
      mmax;
 mmin_index 
   
     =
   
      u;
 }
 }
 
   
     return
   
      sum
   
     +
   
     1
   
     ;
}

   
     int
   
      input()
{
 
   
     int
   
      i,j,tmp,a,b;
 IN(n);

   
     
 tmp 
   
     =
   
      n 
   
     -
   
      
   
     1
   
     ;
 
   
     for
   
     (i 
   
     =
   
      
   
     0
   
     ; i 
   
     <
   
      tmp; 
   
     ++
   
     i)
 {
 scanf(
   
     "
   
     %d %d
   
     "
   
     ,
   
     &
   
     a,
   
     &
   
     b);
 add_edge(a,b);
 }
 
   
     return
   
      
   
     0
   
     ;
}

   
     int
   
      work()
{
 dfs(
   
     1
   
     );
 printf(
   
     "
   
     %d %d\n
   
     "
   
     ,mmin_index,mmin_cnt);
 
   
     return
   
      
   
     0
   
     ;
}


   
     int
   
      main()
{
 
   
     int
   
      i,j,tt,tmp;
 IN(tt);
 
   
     while
   
     (tt
   
     --
   
     )
 {
 init();
  
    
  
    

   
     　　　　 input();

   
     
 work();
 }
 
   
     return
   
      
   
     0
   
     ;
}