poj3006

普通的n^2的筛法居然比线性筛法快，不知道以后该用哪个了……

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

    
      using
    
       
    
      namespace
    
       std;


    
      #define
    
       maxn 1000000
    
      


    
      bool
    
       prime[maxn];


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

    
       memset(prime, 
    
      true
    
      , 
    
      sizeof
    
      (prime));
 
    
      for
    
       (
    
      int
    
       i 
    
      =
    
       
    
      3
    
      ; i 
    
      <=
    
       
    
      1000
    
      ; i 
    
      +=
    
       
    
      2
    
      )
 
    
      for
    
       (
    
      int
    
       j 
    
      =
    
       
    
      3
    
      ; j 
    
      <=
    
       maxn 
    
      /
    
       i; j 
    
      +=
    
       
    
      2
    
      )
 
    
      if
    
       (prime[i])
 prime[i 
    
      *
    
       j] 
    
      =
    
       
    
      false
    
      ;
 
    
      for
    
       (
    
      int
    
       i 
    
      =
    
       
    
      4
    
      ; i 
    
      <=
    
       maxn; i 
    
      +=
    
       
    
      2
    
      )
 prime[i] 
    
      =
    
       
    
      false
    
      ;
 prime[
    
      1
    
      ] 
    
      =
    
       prime[
    
      0
    
      ] 
    
      =
    
       
    
      false
    
      ;

 
    
      int
    
       a, d, n;
 
    
      while
    
       (scanf(
    
      "
    
      %d%d%d
    
      "
    
      , 
    
      &
    
      a, 
    
      &
    
      d, 
    
      &
    
      n) 
    
      !=
    
       EOF 
    
      &&
    
       
    
      !
    
      (a 
    
      ==
    
       
    
      0
    
       
    
      &&
    
       d 
    
      ==
    
       
    
      0
    
       
    
      &&
    
       n 
    
      ==
    
       
    
      0
    
      ))
 {
 
    
      int
    
       p;
 
    
      for
    
       (p 
    
      =
    
       a; n 
    
      >
    
       
    
      0
    
      ; p 
    
      +=
    
       d)
 {
 
    
      if
    
       (prime[p])
 n
    
      --
    
      ;
 }
 printf(
    
      "
    
      %d\n
    
      "
    
      , p 
    
      -
    
       d);
 }
 
    
      return
    
       
    
      0
    
      ;
}