质数检测

1. pub fn prime_check(num: usize) -> bool {
2. if (num > 1) & (num < 4) {
3. return true;
4. } else if (num < 2) || (num % 2 == 0) {
5. return false;
6. }

8. let stop: usize = (num as f64).sqrt() as usize + 1;
9. for i in (3..stop).step_by(2) {
10. if num % i == 0 {
11. return false;
12. }
13. }
14. true
15. }

17. #[cfg(test)]
18. mod tests {
19. use super::*;

21. #[test]
22. fn basic() {
23. assert_eq!(prime_check(3), true);
24. assert_eq!(prime_check(7), true);
25. assert_eq!(prime_check(11), true);
26. assert_eq!(prime_check(2003), true);

28. assert_eq!(prime_check(4), false);
29. assert_eq!(prime_check(6), false);
30. assert_eq!(prime_check(21), false);
31. assert_eq!(prime_check(2004), false);
32. }
33. }