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- <?php
- /*
- * By adding type hints and enabling strict type checking, code can become
- * easier to read, self-documenting and reduce the number of potential bugs.
- * By default, type declarations are non-strict, which means they will attempt
- * to change the original type to match the type specified by the
- * type-declaration.
- *
- * In other words, if you pass a string to a function requiring a float,
- * it will attempt to convert the string value to a float.
- *
- * To enable strict mode, a single declare directive must be placed at the top
- * of the file.
- * This means that the strictness of typing is configured on a per-file basis.
- * This directive not only affects the type declarations of parameters, but also
- * a function's return type.
- *
- * For more info review the Concept on strict type checking in the PHP track
- * <link>.
- *
- * To disable strict typing, comment out the directive below.
- */
- declare(strict_types=1);
- enum State {
- case Maybe;
- case Prime;
- case NotPrime;
- }
- function sieve(int $limit): array {
- $all = [];
- $all[0] = State::NotPrime;
- $all[1] = State::NotPrime;
- for ($i = 2; $i <= $limit; $i++) {
- $all[$i] = State::Maybe;
- }
- for ($i = 2; $i <= $limit; $i++) {
- if ($all[$i] == State::NotPrime) {
- continue;
- }
- $all[$i] = State::Prime;
- for ($j = 2; $j <= $limit / $i; $j++) {
- $all[$i * $j] = State::NotPrime;
- }
- }
- $res = [];
- foreach ($all as $i => $v) {
- if ($v === State::Prime) {
- $res[] = $i;
- }
- }
- return $res;
- }
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