HDU 3371 Connect the Cities

并查集+set容器 Kruskal

  
    

   
     #include 
   
     <
   
     stdio.h
   
     >
   
     
#include 
   
     <
   
     string
   
     .h
   
     >
   
     
#include 
   
     <
   
     set
   
     >
   
     

   
     using
   
      
   
     namespace
   
      std;

   
     const
   
      
   
     int
   
      MAXN 
   
     =
   
      
   
     501
   
     ;

   
     struct
   
      E
{
 
   
     int
   
      x,y;
 
   
     int
   
      weight;
};
E edge[
   
     25001
   
     ];

   
     int
   
      father[MAXN];


   
     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){
 
   
     if
   
     (x 
   
     !=
   
      father[x])
 father[x] 
   
     =
   
      find(father[x]);
 
   
     return
   
      father[x];
}


   
     void
   
      merge(
   
     int
   
      x, 
   
     int
   
      y){
 
   
     if
   
     (x 
   
     >
   
      y){
 father[x] 
   
     =
   
      y;
 } 
   
     else
   
      {
 father[y] 
   
     =
   
      x;
 }
}


   
     int
   
      main(){
 
   
     set
   
     <
   
     int
   
     >
   
      s;
 
   
     int
   
      cas,n,m,k,cost;
 scanf(
   
     "
   
     %d
   
     "
   
     ,
   
     &
   
     cas);
 
   
     while
   
     ( cas
   
     --
   
      ){
 scanf(
   
     "
   
     %d %d %d
   
     "
   
     ,
   
     &
   
     n, 
   
     &
   
     m, 
   
     &
   
     k);
 s.clear();
 makeSet(n);
 cost 
   
     =
   
      
   
     0
   
     ;
 
   
     for
   
     (
   
     int
   
      i 
   
     =
   
      
   
     1
   
     ; i 
   
     <=
   
      m; i
   
     ++
   
     ){
 scanf(
   
     "
   
     %d%d%d
   
     "
   
     ,
   
     &
   
     edge[i].x,
   
     &
   
     edge[i].y,
   
     &
   
     edge[i].weight);
 }
 
   
     int
   
      num,first,city;
 
   
     for
   
     (
   
     int
   
      i 
   
     =
   
      
   
     1
   
     ; i 
   
     <=
   
      k;i
   
     ++
   
     ){
 scanf(
   
     "
   
     %d%d
   
     "
   
     ,
   
     &
   
     num,
   
     &
   
     first);
 
   
     for
   
     (
   
     int
   
      j 
   
     =
   
      
   
     1
   
     ; j 
   
     <
   
      num; j
   
     ++
   
     ){
 scanf(
   
     "
   
     %d
   
     "
   
     ,
   
     &
   
     city);
 
   
     int
   
      xx 
   
     =
   
      find(first);
 
   
     int
   
      yy 
   
     =
   
      find(city);
 
   
     if
   
     (xx 
   
     !=
   
      yy)
 merge(xx,yy);
 }
 }
 qsort(edge
   
     +
   
     1
   
     ,m,
   
     sizeof
   
     (E),cmp);
 
   
     for
   
     (
   
     int
   
      i 
   
     =
   
      
   
     1
   
     ; i 
   
     <=
   
      m; i
   
     ++
   
     ){
 
   
     int
   
      xx 
   
     =
   
      find(edge[i].x);
 
   
     int
   
      yy 
   
     =
   
      find(edge[i].y);
 
   
     if
   
     (xx 
   
     !=
   
      yy){
 merge(xx,yy);
 cost 
   
     +=
   
      edge[i].weight;
 }
 }
 
   
     for
   
     (
   
     int
   
      i 
   
     =
   
      
   
     1
   
     ; i 
   
     <=
   
      n; i
   
     ++
   
     ){
 find(i);
 }
 
   
     for
   
     (
   
     int
   
      i 
   
     =
   
      
   
     1
   
     ; i 
   
     <=
   
      n; i
   
     ++
   
     ){
 s.insert(father[i]);
 }
 
   
     if
   
     (s.size() 
   
     >
   
      
   
     1
   
     ){
 printf(
   
     "
   
     -1\n
   
     "
   
     );
 } 
   
     else
   
      {
 printf(
   
     "
   
     %d\n
   
     "
   
     ,cost);
 }
 }
 
   
     return
   
      
   
     0
   
     ;
}