poj2262

简单题

View Code

   
     

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

    
      using
    
       
    
      namespace
    
       std;


    
      #define
    
       N 1000005
    
      


    
      bool
    
       
    
      is
    
      [N];

    
      int
    
       prm[N];


    
      int
    
       getprm(
    
      int
    
       n)
{
 
    
      int
    
       i, j, k 
    
      =
    
       
    
      0
    
      ;
 
    
      int
    
       s, e 
    
      =
    
       (
    
      int
    
       )(sqrt(
    
      0.0
    
      +
    
      n) 
    
      +
    
      1
    
      );
 memset(
    
      is
    
      , 
    
      1
    
      , 
    
      sizeof
    
      (
    
      is
    
      ));
 prm[k
    
      ++
    
      ] 
    
      =
    
       
    
      2
    
      ; 
    
      is
    
      [
    
      0
    
      ] 
    
      =
    
       
    
      is
    
      [
    
      1
    
      ] 
    
      =
    
       
    
      0
    
      ;
 
    
      for
    
       (i 
    
      =
    
      4
    
      ; i 
    
      <
    
       n; i
    
      +=
    
       
    
      2
    
      ) 
    
      is
    
      [i] 
    
      =
    
       
    
      0
    
      ;
 
    
      for
    
      (i 
    
      =
    
       
    
      3
    
      ; i 
    
      <
    
       e; i
    
      +=
    
      2
    
      )
 
    
      if
    
       (
    
      is
    
      [i])
 {
 prm[k
    
      ++
    
      ] 
    
      =
    
       i;
 
    
      for
    
      (s 
    
      =
    
       i 
    
      *
    
       
    
      2
    
      , j 
    
      =
    
       i 
    
      *
    
       i; j 
    
      <
    
       n; j
    
      +=
    
      s)
 
    
      is
    
      [j] 
    
      =
    
       
    
      0
    
      ;
 }
 
    
      for
    
      (; i 
    
      <
    
       n; i
    
      +=
    
      2
    
      )
 
    
      if
    
       (
    
      is
    
      [i])prm[k
    
      ++
    
      ] 
    
      =
    
       i;
 
    
      return
    
       k;
}


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

    
       
    
      int
    
       tot 
    
      =
    
       getprm(
    
      1000000
    
      );
 
    
      int
    
       n;
 
    
      while
    
       (scanf(
    
      "
    
      %d
    
      "
    
      , 
    
      &
    
      n), n)
 {
 
    
      for
    
       (
    
      int
    
       i 
    
      =
    
       
    
      0
    
      ; i 
    
      <
    
       tot 
    
      &&
    
       prm[i] 
    
      *
    
       
    
      2
    
       
    
      <=
    
       n; i
    
      ++
    
      )
 
    
      if
    
       (
    
      is
    
      [n 
    
      -
    
       prm[i]])
 {
 printf(
    
      "
    
      %d = %d + %d\n
    
      "
    
      , n, prm[i], n 
    
      -
    
       prm[i]);
 
    
      break
    
      ;
 }
 }
 
    
      return
    
       
    
      0
    
      ;
}