C++ Program pf seiving numbers

Here's the program. As usual, if you need details, see
http://mathmate.brinkster.net/
and look under programming.

#include < stdio.h>
#include < stdlib.h>
#include < math.h>
int main(int argc, char *argv[])
{
int a[301],i,j;
for(i=0;i<=300;i++)a[i]=1; // initialize, 1=prime, 0=composite
for(i=2;i<=sqrt(300);i++)
{
// skip over composites
if(a[i]!=0)for(j=2*i;j<=300;j+=i) a[j]=0;
// mark multiples of primes except first
}
// print primes
for(i=1;i<=300;i++)if(a[i]!=0)printf("%d ",i);
}


2008-01-19 21:56:27 補充：
The above code is based on making an array of numbers from 1 to 300, all initialized to 1. Starting from 2, multiples of 2 (4,6,8,...)are marked zero (composite). Then it proceeds to the next number if it is not a composite.

2008-01-19 21:56:59 補充：
For 3, it marks zero for 6,9,12,15.... Four (4) has previously been marked composite, so it will not be necessary to mark multiples. This will continue until the square root of 300 (17), which is the maximum integer whose square is below 300.