feat: Add Aliquot Sum implementation (TheAlgorithms#412)

src/math/aliquot_sum.rs

@@ -0,0 +1,40 @@
+/// Aliquot sum of a number is defined as the sum of the proper divisors of
+/// a number, i.e. all the divisors of a number apart from the number itself
+/// For example: The aliquot sum of 6 is (1 + 2 + 3) = 6, and that of 15 is
+/// (1 + 3 + 5) = 9
+/// Wikipedia article on Aliquot Sum: https://en.wikipedia.org/wiki/Aliquot_sum
+
+pub fn aliquot_sum(number: u64) -> u64 {
+    if number == 1 || number == 0 {
+        return 0;
+    }
+    let mut sum: u64 = 0;
+
+    for i in 1..(number / 2 + 1) {
+        if number % i == 0 {
+            sum += i;
+        }
+    }
+
+    sum
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn one_digit_number() {
+        assert_eq!(aliquot_sum(6), 6);
+    }
+
+    #[test]
+    fn two_digit_number() {
+        assert_eq!(aliquot_sum(15), 9);
+    }
+
+    #[test]
+    fn three_digit_number() {
+        assert_eq!(aliquot_sum(343), 57);
+    }
+}

src/math/mod.rs

@@ -1,3 +1,4 @@
+mod aliquot_sum;
 mod amicable_numbers;
 mod armstrong_number;
 mod baby_step_giant_step;
@@ -35,6 +36,7 @@ mod square_root;
 mod trial_division;
 mod zellers_congruence_algorithm;
 
+pub use self::aliquot_sum::aliquot_sum;
 pub use self::amicable_numbers::amicable_pairs_under_n;
 pub use self::armstrong_number::is_armstrong_number;
 pub use self::baby_step_giant_step::baby_step_giant_step;