N以内素数算法

1、?phpheader(content-type:text/html; charset=utf-8);/这是最简单，但也是效率最低的算法，后面是优化后的算法，整个文档可以存为php文件直接用浏览器打开/ $num = 10000;/ $total = 1;/ for( $i = 3; $i $num; $i = $i + 2 )/ / for( $j = 3; $j $i; $j = $j + 2 )/ / if( $i % $j = 0 )/ / break;/ ;/ ;/ if( $i = $j )/ / $total+;/ echo $i.;/ ;/ ;/ echo $total;func

2、tion prime( $num, $pre_primes = array(1,2,3) )if( $num = 2 ) return array(1,2);if( $num = 1 ) return array(1);if( $num = 0 ) return array();$last = $pre_primescount($pre_primes) - 1;for( $i = $last + 2; $i = $num; $i = $i + 2 )if( $i % 10 = 5 ) continue;for( $j = 2; $j = $sq | $i % $prime = 0 )break

3、;if( $prime = $sq )$pre_primes = $i;if( $i $num - 1 )return prime( $num, $pre_primes );elsereturn $pre_primes;/ $a = prime(100000);/ echo (count($a).;/ print_r( join( , $a ) );/ echo ;?N以内的质数个数function prime( num, pre_primes )switch( num )case 0:return ;break;case 1:return 1;break;case 2:return 1,2;

4、break;default:var pre_primes = pre_primes | 1,2,3;var last = pre_primes.slice( -1 )0;var i,j,prime;for( i = last + 2; i = num; i = i + 2 )if( i % 10 = 5 ) continue;for( j = 2; j = sq )break;if( prime = sq )pre_primes.push(i);if( i num - 1 )return prime( num, pre_primes );elsereturn pre_primes;break;

5、/ document.write( prime(100000).length );function get_prime_arr( n, p )var p = p | 5,2,3;var last = p.slice( -1 )0;var i,j,prime;for( i = last + 2; i = n; i = i + 2 )if( i % 10 = 5 ) continue;for( j = 2; j = sq )break;if( prime = sq )p.push(i);if( i n )document.getElementById(d).innerHTML = ( p.length );clearInterval( timer1 );if( m % 10 = 5 ) return;for( i = 1; i = sq )break;if( prime = sq )p.push(m);, 1);var input = document.getElementById(num);var submit = document.getElementById(submit);submit.