hdu 1045Fire Net(DFS or 二分匹配)

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      //
    
      数据小,dfs+回溯,能够水过
    
      

    
      #include 
    
      <
    
      iostream
    
      >
    
      
#include 
    
      <
    
      cstring
    
      >
    
      
#include 
    
      <
    
      queue
    
      >
    
      


    
      using
    
       
    
      namespace
    
       std;

    
      const
    
       
    
      int
    
       MAX 
    
      =
    
       
    
      10
    
      ;

    
      char
    
       map[MAX][MAX];

    
      int
    
       n,ans;


    
      bool
    
       can(
    
      int
    
       x,
    
      int
    
       y)
{
 
    
      int
    
       i,j;

 
    
      for
    
      (i 
    
      =
    
       x
    
      +
    
      1
    
      ;i 
    
      <
    
       n;
    
      ++
    
      i)
 {
 
    
      if
    
      (map[i][y] 
    
      ==
    
       
    
      '
    
      Z
    
      '
    
      ) 
    
      return
    
       
    
      false
    
      ;
 
    
      if
    
      (map[i][y] 
    
      ==
    
       
    
      '
    
      X
    
      '
    
      ) 
    
      break
    
      ;
 }
 
    
      for
    
      (i 
    
      =
    
       
    
      0
    
      ;i 
    
      <
    
       x;
    
      ++
    
      i)
 {
 
    
      if
    
      (map[i][y] 
    
      ==
    
       
    
      '
    
      Z
    
      '
    
      ) 
    
      return
    
       
    
      false
    
      ;
 
    
      if
    
      (map[i][y] 
    
      ==
    
       
    
      '
    
      X
    
      '
    
      ) 
    
      break
    
      ;
 }

 
    
      for
    
      (j 
    
      =
    
       
    
      0
    
      ;j 
    
      <
    
       y;
    
      ++
    
      j)
 {
 
    
      if
    
      (map[x][j] 
    
      ==
    
       
    
      '
    
      Z
    
      '
    
      ) 
    
      return
    
       
    
      false
    
      ;
 
    
      if
    
      (map[x][j] 
    
      ==
    
       
    
      '
    
      X
    
      '
    
      ) 
    
      break
    
      ;
 }

 
    
      for
    
      (j 
    
      =
    
       y
    
      +
    
      1
    
      ;j 
    
      <
    
       n;
    
      ++
    
      j)
 {
 
    
      if
    
      (map[x][j] 
    
      ==
    
       
    
      '
    
      Z
    
      '
    
      ) 
    
      return
    
       
    
      false
    
      ;
 
    
      if
    
      (map[x][j] 
    
      ==
    
       
    
      '
    
      X
    
      '
    
      ) 
    
      break
    
      ;
 }

 
    
      return
    
       
    
      true
    
      ;
}


    
      void
    
       dfs(
    
      int
    
       sum)
{
 
    
      for
    
      (
    
      int
    
       i 
    
      =
    
       
    
      0
    
      ;i 
    
      <
    
       n;
    
      ++
    
      i)
 {
 
    
      for
    
      (
    
      int
    
       j 
    
      =
    
       
    
      0
    
      ;j 
    
      <
    
       n;
    
      ++
    
      j)
 {
 
    
      if
    
      (map[i][j] 
    
      ==
    
       
    
      '
    
      .
    
      '
    
       
    
      &&
    
       can(i,j))
 {
 map[i][j] 
    
      =
    
       
    
      '
    
      Z
    
      '
    
      ;
 dfs(sum
    
      +
    
      1
    
      );
 map[i][j] 
    
      =
    
       
    
      '
    
      .
    
      '
    
      ;
 }

 
    
      if
    
      (i 
    
      ==
    
       n
    
      -
    
      1
    
       
    
      &&
    
       j 
    
      ==
    
       n
    
      -
    
      1
    
      )
 {
 
    
      if
    
      (sum 
    
      >
    
       ans) ans 
    
      =
    
       sum;
 
    
      return
    
      ;
 }
 }
 }
}



    
      int
    
       main()
{
 
    
      int
    
       i;

 
    
      while
    
      (scanf(
    
      "
    
      %d
    
      "
    
      ,
    
      &
    
      n),n 
    
      !=
    
       
    
      0
    
      )
 {
 
    
      for
    
      (i 
    
      =
    
       
    
      0
    
      ;i 
    
      <
    
       n;
    
      ++
    
      i) scanf(
    
      "
    
      %s
    
      "
    
      ,map[i]);

 ans 
    
      =
    
       
    
      -
    
      2000000
    
      ; dfs(
    
      0
    
      );

 cout
    
      <<
    
      ans
    
      <<
    
      endl;
 }

 
    
      return
    
       
    
      0
    
      ;
}