hdu2553

http://acm.hdu.edu.cn/showproblem.php?pid=2553

 Nqueen问题

   
     

    
      #include
    
      "
    
      iostream
    
      "
    
      

    
      using
    
       
    
      namespace
    
       std;

    
      int
    
       n;

    
      int
    
       a[
    
      20
    
      ];

    
      int
    
       b[
    
      20
    
      ];

    
      int
    
       c;

    
      bool
    
       Panduan(
    
      int
    
       x)
{
 
    
      for
    
      (
    
      int
    
       i
    
      =
    
      0
    
      ; i
    
      <
    
      x; i
    
      ++
    
      )
 {
 
    
      if
    
      ( (a[x]
    
      -
    
      a[i])
    
      ==
    
      0
    
       
    
      ||
    
       (abs(a[x]
    
      -
    
      a[i])
    
      -
    
      abs(x
    
      -
    
      i))
    
      ==
    
      0
    
       ) 
    
      return
    
       
    
      false
    
      ; //关键点
 }
 
    
      return
    
       
    
      true
    
      ;
}


    
      void
    
       dfs(
    
      int
    
       y ,
    
      int
    
       z)
{
 
    
      for
    
      (
    
      int
    
       p
    
      =
    
      0
    
      ; p
    
      <
    
      z; p
    
      ++
    
      )
 {
 a[y]
    
      =
    
      p;
 
 
    
      if
    
      (Panduan(y))
 {
 
    
      if
    
      (y 
    
      ==
    
       z
    
      -
    
      1
    
      ) c
    
      ++
    
      ;
 
    
      else
    
       dfs(y
    
      +
    
      1
    
      ,z);
 }
 }
}

    
      int
    
       main()
{
 
    
      for
    
      (
    
      int
    
       q
    
      =
    
      1
    
      ;q
    
      <=
    
      10
    
      ;q
    
      ++
    
      )
 {
 c
    
      =
    
      0
    
      ;
 dfs(
    
      0
    
       , q);
 b[q]
    
      =
    
      c;
 }
 
    
      while
    
      (cin
    
      >>
    
      n,n)
 {
 cout
    
      <<
    
      b[n]
    
      <<
    
      endl;
 }
 
    
      return
    
       
    
      0
    
      ; 
}