HDU 1233 畅通工程2

  
    

   
     //最基础的
   
     并查集 最小生成树 
   
     

   
     #include 
   
     <
   
     stdio.h
   
     >
   
     
#include 
   
     <
   
     stdlib.h
   
     >
   
      

   
     const
   
      
   
     int
   
      MAX 
   
     =
   
      
   
     101
   
     ;

   
     struct
   
      E{
 
   
     int
   
      x,y,weight;
};
E edge[
   
     5001
   
     ];

   
     int
   
      father[MAX];

   
     int
   
      cmp(
   
     const
   
      
   
     void
   
      
   
     *
   
     d1, 
   
     const
   
      
   
     void
   
      
   
     *
   
     d2){
 
   
     return
   
      (
   
     *
   
     (E
   
     *
   
     )d1).weight 
   
     -
   
      (
   
     *
   
     (E
   
     *
   
     )d2).weight;
}

   
     void
   
      makeSet(
   
     int
   
      n){
 
   
     for
   
     (
   
     int
   
      i 
   
     =
   
      
   
     0
   
     ; i 
   
     <=
   
      n; i
   
     ++
   
     )
 father[i] 
   
     =
   
      i;
}

   
     int
   
      find(
   
     int
   
      x){
 
   
     return
   
      father[x] 
   
     ==
   
      x 
   
     ?
   
      x : father[x] 
   
     =
   
      find(father[x]);
}

   
     int
   
      main(){
 
   
     int
   
      N,cost;
 
   
     while
   
     (scanf(
   
     "
   
     %d
   
     "
   
     ,
   
     &
   
     N) 
   
     ==
   
      
   
     1
   
     ){
 
   
     if
   
     (N 
   
     ==
   
      
   
     0
   
     )
 
   
     break
   
     ;
 makeSet(N);
 cost 
   
     =
   
      
   
     0
   
     ;
 
   
     for
   
     (
   
     int
   
      i 
   
     =
   
      
   
     1
   
     ; i 
   
     <=
   
      N
   
     *
   
     (N
   
     -
   
     1
   
     )
   
     /
   
     2
   
     ; i
   
     ++
   
     ){
 scanf(
   
     "
   
     %d%d%d
   
     "
   
     ,
   
     &
   
     edge[i].x,
   
     &
   
     edge[i].y,
   
     &
   
     edge[i].weight);
 }
 qsort(edge
   
     +
   
     1
   
     ,N
   
     *
   
     (N
   
     -
   
     1
   
     )
   
     /
   
     2
   
     ,
   
     sizeof
   
     (E),cmp); 
   
     //
   
     一开始写成edge 一直错 因为0号单元没用 
   
     

   
      
   
     for
   
     (
   
     int
   
      i 
   
     =
   
      
   
     1
   
     ; i 
   
     <=
   
      N
   
     *
   
     (N
   
     -
   
     1
   
     )
   
     /
   
     2
   
     ; i
   
     ++
   
     ){
 
   
     int
   
      x 
   
     =
   
      find(edge[i].x);
 
   
     int
   
      y 
   
     =
   
      find(edge[i].y);
 
   
     if
   
     (x 
   
     !=
   
      y ){
 cost 
   
     +=
   
      edge[i].weight;
 
   
     if
   
     (x 
   
     >
   
      y)
 father[x] 
   
     =
   
      y;
 
   
     else
   
     
 father[y] 
   
     =
   
      x;
 }
 }
 printf(
   
     "
   
     %d\n
   
     "
   
     ,cost);
 }
 
   
     return
   
      
   
     0
   
     ;
}