poj2531

暴力搜索dfs，注意要利用递归来减少计算总通信量的次数。

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

    
      using
    
       
    
      namespace
    
       std;


    
      #define
    
       maxn 21
    
      


    
      int
    
       map[maxn][maxn], ans 
    
      =
    
       
    
      0
    
      ;

    
      bool
    
       
    
      in
    
      [maxn];

    
      int
    
       n;


    
      void
    
       dfs(
    
      int
    
       now, 
    
      int
    
       sum)
{
 
    
      if
    
       (now 
    
      >
    
       n)
 {
 
    
      if
    
       (sum 
    
      >
    
       ans)
 ans 
    
      =
    
       sum;
 
    
      return
    
      ;
 }
 
    
      in
    
      [now] 
    
      =
    
       
    
      true
    
      ;
 
    
      int
    
       add 
    
      =
    
       
    
      0
    
      ;
 
    
      for
    
       (
    
      int
    
       i 
    
      =
    
       
    
      0
    
      ; i 
    
      <
    
       now; i
    
      ++
    
      )
 
    
      if
    
       (
    
      !
    
      in
    
      [i])
 add 
    
      +=
    
       map[i][now];
 dfs(now 
    
      +
    
       
    
      1
    
      , add 
    
      +
    
       sum);

 
    
      in
    
      [now] 
    
      =
    
       
    
      false
    
      ;
 add 
    
      =
    
       
    
      0
    
      ;
 
    
      for
    
       (
    
      int
    
       i 
    
      =
    
       
    
      0
    
      ; i 
    
      <
    
       now; i
    
      ++
    
      )
 
    
      if
    
       (
    
      in
    
      [i])
 add 
    
      +=
    
       map[i][now];
 dfs(now 
    
      +
    
       
    
      1
    
      , add 
    
      +
    
       sum);
}


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

    
       scanf(
    
      "
    
      %d
    
      "
    
      , 
    
      &
    
      n);
 
    
      for
    
       (
    
      int
    
       i 
    
      =
    
       
    
      0
    
      ; i 
    
      <
    
       n; i
    
      ++
    
      )
 
    
      for
    
       (
    
      int
    
       j 
    
      =
    
       
    
      0
    
      ; j 
    
      <
    
       n; j
    
      ++
    
      )
 scanf(
    
      "
    
      %d
    
      "
    
      , 
    
      &
    
      map[i][j]);
 dfs(
    
      0
    
      , 
    
      0
    
      );
 printf(
    
      "
    
      %d\n
    
      "
    
      , ans);
 
    
      return
    
       
    
      0
    
      ;
}