求100以内的质数

今天看博客园的时候看到这个问题，突然想起自己又很久没有关注过算法了。印象中这个是写过的，一个是利用开方来解决，一个是利用筛选来解决，还有个利用bitarray的筛选法。复习了下，代码如下：

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using System;   class FindPrime { static void Main() {     prime_while();     Console.WriteLine();     prime_array(); }       public static void prime_while()     {         const int Max = 100;         Console.Write("2 ");         int n=1,k=3;         do{           int j = (int)Math.Sqrt(k);           if(j%2==0)              j--;           bool isPrime=true;           while(j>2 && isPrime)               if(k%j==0)                 isPrime=false;               else                 j-=2;           if(isPrime)           {              n++;              Console.Write(k+" ");           }           k+=2;           }while(k<=Max);       }         public static void prime_array()     {        const int Max = 100;        int[] prime = new int[30];        prime[0]=2;        int n=1,k=3,i=1;        do{           int j=0;           while(j<n && k%prime[j]!=0)           {                j++;           }           if(j==n)           {              prime[i]=k;              i++;              n++;           }            k+=2;          }while(k<=Max);          for(int m=0;m<prime.Length;m++)             Console.Write(prime[m]+" ");     } }