Question

如何使用指定的接口为素数生成器编写代码。

Answer 1

我认为这就是你所问的。

int isPrime(int i) {
    int j;
    if(i == 1 || i == 2)
            return 1;
    if(i % 2 == 0)
            return 0;

    for (j = 3; j < sqrt(n); j += 2)
            if (i % j == 0)
                    return 0;

    return 1;
}

void generator(int start, int end) {
    int i;
    if(start > end) {
            int temp = start;
            start = end;
            end = start;
    }

    for (i = start; i<=end; i++)
            if(isPrime(i))
                    printf("%d\n", i);
}

int main() {
    generator(7900, 7920);
    return 0;
}

Answer 2

在这里，它确实在最后做了一件有趣的事情，但它确实有效。你可以在http://operationwalrus.com/primeval.php?x=1&y=100

看到它的实际效果

<?
$x = $_GET['x'];
$y = $_GET['y'];
//$x and $y must be ordered acendingly
if ($x > $y) {
    $temp = $x;
    $x = $y;
    $y = $temp;
}
$num = range($x, $y);
sort($num);
$arr = (findPrimeValues($num, $x, $y));
$arr = array_values(array_filter($arr));
for ($i=0;$i <= $y+1;$i++) {
    $prnt = $arr[$i] . ', ';
    str_replace(', ,', "",$prnt);
    print_r($prnt);
}
function findPrimeValues($num, $x, $y) {
    //1 is not prime. See: http://en.wikipedia.org/wiki/Prime_number#Primality_of_one
    $pos = array_search(1, $num);
    if (is_int($pos)) {
        unset($num[$pos]);
    }

    /**
     * if a number in the range is divisible by two and its not two, then it's
     * not prime and it's removed from the array.
     */
    for ($i=$x;$i <= $y;$i++) { 
        if (($i !== 2) && ($i % 2 == 0)) {
            $pos = array_search($i, $num);
            unset($num[$pos]);
        }
    }

    /**
     * Checks the odd numbers. If any of them is a factor, then it returns false.
     * The sqrt can be an aproximation, hence just for the sake of
     * security, one rounds it to the next highest integer value.
     * $u is the number we are testing against.
     */
    for ($u=$x;$u <= $y; $u++) {
        for ($i = 3; $i <= ceil(sqrt($u)); $i = $u + 2) {      
            if($u % $i == 0) {
                $pos = array_search($u, $num);
                unset($num[$pos]);
            }
        }
    }
    return($num);
}

使用接口的素数

2 个答案: