HDU 1863 畅通工程

读入边权要注意是否比原来的边权小

  
    

   
     #include 
   
     <
   
     iostream
   
     >
   
     
#include 
   
     <
   
     fstream
   
     >
   
     
#include 
   
     <
   
     string
   
     .h
   
     >
   
     

   
     using
   
      
   
     namespace
   
      std;

   
     const
   
      
   
     int
   
      MAXN 
   
     =
   
      
   
     1000
   
     ;

   
     int
   
      G[MAXN][MAXN];

   
     int
   
      lowcost[MAXN];

   
     int
   
      cloest[MAXN];

   
     bool
   
      used[MAXN];

   
     int
   
      cost;


   
     void
   
      PRIM(
   
     int
   
      n){
 
   
     int
   
      cnt 
   
     =
   
      
   
     0
   
     ;
 cost 
   
     =
   
      
   
     0
   
     ;
 used[
   
     1
   
     ] 
   
     =
   
      
   
     true
   
     ;
 
   
     for
   
     (
   
     int
   
      i 
   
     =
   
      
   
     2
   
     ; i 
   
     <=
   
      n; i
   
     ++
   
     ){
 lowcost[i] 
   
     =
   
      G[i][
   
     1
   
     ];
 cloest[i] 
   
     =
   
      
   
     1
   
     ;
 used[i] 
   
     =
   
      
   
     false
   
     ;
 }
 
   
     for
   
     (
   
     int
   
      i 
   
     =
   
      
   
     1
   
     ; i 
   
     <
   
      n; i
   
     ++
   
     ){
 
   
     int
   
      min 
   
     =
   
      
   
     32767
   
     , minIndex 
   
     =
   
      i;
 
   
     for
   
     (
   
     int
   
      j 
   
     =
   
      
   
     1
   
     ; j 
   
     <=
   
      n; j
   
     ++
   
     ){
 
   
     if
   
     ( 
   
     !
   
     used[j] 
   
     &&
   
      lowcost[j] 
   
     <
   
      min){
 min 
   
     =
   
      lowcost[j];
 minIndex 
   
     =
   
      j;
 }
 }
 
   
     if
   
     (min 
   
     ==
   
      
   
     32767
   
     ){
 
   
     break
   
     ;
 }
 cost 
   
     +=
   
      min;
 used[minIndex] 
   
     =
   
      
   
     true
   
     ;
 cnt
   
     ++
   
     ;
 
   
     for
   
     (
   
     int
   
      j 
   
     =
   
      
   
     1
   
     ; j 
   
     <=
   
      n; j
   
     ++
   
     ){
 
   
     if
   
     ( 
   
     !
   
     used[j] 
   
     &&
   
      lowcost[j] 
   
     >
   
      G[minIndex][j]){
 lowcost[j] 
   
     =
   
      G[minIndex][j];
 cloest[j] 
   
     =
   
      minIndex;
 }
 }
 }
 
   
     if
   
     ( cnt 
   
     !=
   
      n 
   
     -
   
      
   
     1
   
     )
 cout 
   
     <<
   
      
   
     "
   
     ?
   
     "
   
      
   
     <<
   
      endl;
 
   
     else
   
     
 cout 
   
     <<
   
      cost 
   
     <<
   
      endl;
}


   
     int
   
      main(){
 
   
     int
   
      n, m, x, y, weight;
 
   
     while
   
     (cin 
   
     >>
   
      n 
   
     >>
   
      m){
 
   
     if
   
     ( n 
   
     ==
   
      
   
     0
   
     )
 
   
     break
   
     ;
 
   
     //
   
     memset(G,32767,sizeof(G));
   
     

   
      
   
     for
   
     (
   
     int
   
      i 
   
     =
   
      
   
     0
   
     ; i 
   
     <
   
      
   
     1000
   
     ; 
   
     ++
   
     i)
 
   
     for
   
     (
   
     int
   
      j 
   
     =
   
      
   
     0
   
     ; j 
   
     <
   
      
   
     1000
   
     ; 
   
     ++
   
     j){
 G[i][j] 
   
     =
   
      
   
     32767
   
     ;
 }
 
   
     for
   
     (
   
     int
   
      i 
   
     =
   
      
   
     1
   
     ; i 
   
     <=
   
      n;i
   
     ++
   
     ){
 cin 
   
     >>
   
      x 
   
     >>
   
      y 
   
     >>
   
      weight;
 G[x][y] 
   
     =
   
      G[x][y] 
   
     <
   
      weight 
   
     ?
   
      G[x][y]:weight; 
   
     //
   
     陷阱
   
     

   
      G[y][x] 
   
     =
   
      G[x][y];
 
   
     //
   
     G[x][y] = G[x][y] < weight ? G[x][y]:weight;
 
   
     //
   
     G[y][x] = G[x][y] = weight;
   
     

   
      }
 
   
     //
   
     cout << cost << endl;
   
     

   
      
   
     if
   
     ( n 
   
     <
   
      m 
   
     -
   
      
   
     1
   
     )
 cout 
   
     <<
   
      
   
     "
   
     ?
   
     "
   
      
   
     <<
   
      endl;
 
   
     else
   
     
 PRIM(m);
 }
 
   
     return
   
      
   
     0
   
     ;
}