poj2485

最小生成树

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      #include 
    
      <
    
      iostream
    
      >
    
      
#include 
    
      <
    
      cstdio
    
      >
    
      
#include 
    
      <
    
      cstdlib
    
      >
    
      
#include 
    
      <
    
      cstring
    
      >
    
      

    
      using
    
       
    
      namespace
    
       std;


    
      #define
    
       maxn 505
    
      

    
      #define
    
       inf 0x3f3f3f3f
    
      


    
      int
    
       n, cost[maxn][maxn];

    
      bool
    
       vis[maxn];

    
      int
    
       lowcost[maxn];


    
      void
    
       input()
{
 scanf(
    
      "
    
      %d
    
      "
    
      , 
    
      &
    
      n);
 
    
      for
    
       (
    
      int
    
       i 
    
      =
    
       
    
      0
    
      ; i 
    
      <
    
       n; i
    
      ++
    
      )
 
    
      for
    
       (
    
      int
    
       j 
    
      =
    
       
    
      0
    
      ; j 
    
      <
    
       n; j
    
      ++
    
      )
 scanf(
    
      "
    
      %d
    
      "
    
      , 
    
      &
    
      cost[i][j]);
}


    
      int
    
       prim()
{
 
    
      int
    
       ret 
    
      =
    
       
    
      0
    
      , pre, best;

 memset(vis, 
    
      0
    
      , 
    
      sizeof
    
      (vis));
 
    
      for
    
       (
    
      int
    
       i 
    
      =
    
       
    
      0
    
      ; i 
    
      <
    
       n; i
    
      ++
    
      )
 lowcost[i] 
    
      =
    
       inf;
 lowcost[
    
      0
    
      ] 
    
      =
    
       
    
      0
    
      ;
 vis[
    
      0
    
      ] 
    
      =
    
       
    
      true
    
      ;
 pre 
    
      =
    
       
    
      0
    
      ;
 
    
      while
    
       (
    
      1
    
      )
 {
 
    
      for
    
       (
    
      int
    
       i 
    
      =
    
       
    
      0
    
      ; i 
    
      <
    
       n; i
    
      ++
    
      )
 
    
      if
    
       (
    
      !
    
      vis[i] 
    
      &&
    
       lowcost[i] 
    
      >
    
       cost[pre][i])
 lowcost[i] 
    
      =
    
       cost[pre][i];
 best 
    
      =
    
       inf;
 pre 
    
      =
    
       
    
      -
    
      1
    
      ;
 
    
      for
    
       (
    
      int
    
       i 
    
      =
    
       
    
      0
    
      ; i 
    
      <
    
       n; i
    
      ++
    
      )
 
    
      if
    
       (
    
      !
    
      vis[i] 
    
      &&
    
       lowcost[i] 
    
      <
    
       best)
 {
 pre 
    
      =
    
       i;
 best 
    
      =
    
       lowcost[i];
 }
 
    
      if
    
       (pre 
    
      ==
    
       
    
      -
    
      1
    
      )
 
    
      break
    
      ;
 vis[pre] 
    
      =
    
       
    
      true
    
      ;
 ret 
    
      =
    
       max(ret, lowcost[pre]);
 lowcost[pre] 
    
      =
    
       
    
      0
    
      ;
 }
 
    
      return
    
       ret;
}


    
      int
    
       main()
{
 
    
      //
    
      freopen("t.txt", "r", stdin);
    
      

    
       
    
      int
    
       t;
 scanf(
    
      "
    
      %d
    
      "
    
      , 
    
      &
    
      t);
 
    
      while
    
       (t
    
      --
    
      )
 {
 input();
 printf(
    
      "
    
      %d\n
    
      "
    
      , prim());
 }
 
    
      return
    
       
    
      0
    
      ;
}