poj1850

组合数学

View Code

   
     

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

    
      using
    
       
    
      namespace
    
       std;


    
      char
    
       st[
    
      15
    
      ];


    
      int
    
       com(
    
      int
    
       n, 
    
      int
    
       r)
{
 
    
      if
    
       (n 
    
      -
    
       r 
    
      <
    
       r)
 r 
    
      =
    
       n 
    
      -
    
       r;
 
    
      int
    
       i, j, s 
    
      =
    
       
    
      1
    
      ;
 
    
      for
    
       (i 
    
      =
    
       
    
      0
    
      , j 
    
      =
    
       
    
      1
    
      ; i 
    
      <
    
       r; 
    
      ++
    
      i)
 {
 s 
    
      *=
    
       (n 
    
      -
    
       i);
 
    
      for
    
       (; j 
    
      <=
    
       r 
    
      &&
    
       s 
    
      %
    
       j 
    
      ==
    
       
    
      0
    
      ; 
    
      ++
    
      j)
 s 
    
      /=
    
       j;
 }
 
    
      return
    
       s;
}


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

    
       gets(st);
 
    
      int
    
       len 
    
      =
    
       strlen(st);
 
    
      if
    
       (len 
    
      ==
    
       
    
      1
    
      )
 {
 printf(
    
      "
    
      %d\n
    
      "
    
      , st[
    
      0
    
      ] 
    
      -
    
       
    
      '
    
      a
    
      '
    
       
    
      +
    
       
    
      1
    
      );
 
    
      return
    
       
    
      0
    
      ;
 }
 
    
      bool
    
       ok 
    
      =
    
       
    
      true
    
      ;
 
    
      if
    
       (st[
    
      0
    
      ] 
    
      <=
    
       
    
      '
    
      z
    
      '
    
       
    
      &&
    
       st[
    
      0
    
      ] 
    
      >=
    
       
    
      '
    
      a
    
      '
    
      )
 ok 
    
      =
    
       
    
      true
    
      ;
 
    
      else
    
      
 ok 
    
      =
    
       
    
      false
    
      ;
 
    
      for
    
       (
    
      int
    
       i 
    
      =
    
       
    
      1
    
      ; i 
    
      <
    
       len; i
    
      ++
    
      )
 
    
      if
    
       (
    
      !
    
      (st[i] 
    
      <=
    
       
    
      '
    
      z
    
      '
    
       
    
      &&
    
       st[i] 
    
      >=
    
       
    
      '
    
      a
    
      '
    
       
    
      &&
    
       st[i] 
    
      >
    
       st[i 
    
      -
    
       
    
      1
    
      ]))
 ok 
    
      =
    
       
    
      false
    
      ;
 
    
      if
    
       (
    
      !
    
      ok)
 {
 printf(
    
      "
    
      0\n
    
      "
    
      );
 
    
      return
    
       
    
      0
    
      ;
 }
 
    
      int
    
       ans 
    
      =
    
       
    
      26
    
      ;
 
    
      for
    
       (
    
      int
    
       i 
    
      =
    
       
    
      2
    
      ; i 
    
      <
    
       len; i
    
      ++
    
      )
 ans 
    
      +=
    
       com(
    
      26
    
      , i);
 ans 
    
      +=
    
       com(
    
      26
    
      , len) 
    
      -
    
       com(
    
      26
    
       
    
      -
    
       (st[
    
      0
    
      ] 
    
      -
    
       
    
      '
    
      a
    
      '
    
      ), len);
 
    
      for
    
       (
    
      int
    
       i 
    
      =
    
       
    
      1
    
      ; i 
    
      <
    
       len; i
    
      ++
    
      )
 ans 
    
      +=
    
       com(
    
      26
    
       
    
      -
    
       (st[i 
    
      -
    
       
    
      1
    
      ] 
    
      -
    
       
    
      '
    
      a
    
      '
    
       
    
      +
    
       
    
      1
    
      ), len 
    
      -
    
       i) 
    
      -
    
       com(
    
      26
    
       
    
      -
    
       (st[i] 
    
      -
    
       
    
      '
    
      a
    
      '
    
      
 ), len 
    
      -
    
       i);
 printf(
    
      "
    
      %d\n
    
      "
    
      , ans 
    
      +
    
       
    
      1
    
      );
 
    
      return
    
       
    
      0
    
      ;
}