寻找完美数

  1. pub fn is_perfect_number(num: usize) -> bool {
  2.     let mut sum = 0;
  4.     for i in 1..num - 1 {
  5.         if num % i == 0 {
  6.             sum += i;
  7.         }
  8.     }
  10.     num == sum
  11. }
  13. pub fn perfect_numbers(max: usize) -> Vec<usize> {
  14.     let mut result: Vec<usize> = Vec::new();
  16.     // It is not known if there are any odd perfect numbers, so we go around all the numbers.
  17.     for i in 1..max + 1 {
  18.         if is_perfect_number(i) {
  19.             result.push(i);
  20.         }
  21.     }
  23.     result
  24. }
  26. #[cfg(test)]
  27. mod tests {
  28.     use super::*;
  30.     #[test]
  31.     fn basic() {
  32.         assert_eq!(is_perfect_number(6), true);
  33.         assert_eq!(is_perfect_number(28), true);
  34.         assert_eq!(is_perfect_number(496), true);
  35.         assert_eq!(is_perfect_number(8128), true);
  37.         assert_eq!(is_perfect_number(5), false);
  38.         assert_eq!(is_perfect_number(86), false);
  39.         assert_eq!(is_perfect_number(497), false);
  40.         assert_eq!(is_perfect_number(8120), false);
  42.         assert_eq!(perfect_numbers(10), vec![6]);
  43.         assert_eq!(perfect_numbers(100), vec![6, 28]);
  44.         assert_eq!(perfect_numbers(496), vec![6, 28, 496]);
  45.         assert_eq!(perfect_numbers(1000), vec![6, 28, 496]);
  46.     }
  47. }