kata(5kyu): add some egyptians fractions

Signed-off-by: Matej Focko <mfocko@redhat.com>

5kyu/some_egyptians_fractions/solution.rs

@@ -0,0 +1,66 @@
+use std::cmp::max;
+use std::cmp::min;
+
+fn gcd(mut a: u32, mut b: u32) -> u32 {
+    while b != 0 {
+        let t = b;
+        b = a % b;
+        a = t;
+    }
+
+    a
+}
+
+fn lcm(a: u32, b: u32) -> u32 {
+    let c = gcd(a, b);
+
+    max(a, b) / c * min(a, b)
+}
+
+fn format_fraction(fraction: &(u32, u32)) -> String {
+    if fraction.1 == 1 {
+        return format!("{}", fraction.0);
+    }
+
+    format!("{}/{}", fraction.0, fraction.1)
+}
+
+fn decompose(mut num: u32, mut denom: u32) -> String {
+    if num == 0 {
+        return "".to_string();
+    }
+
+    let mut fractions: Vec<(u32, u32)> = Vec::new();
+
+    if num >= denom {
+        fractions.push((num / denom, 1));
+        num = num % denom;
+    }
+
+    let mut running_denom = 2;
+    while num > 1 {
+        if num * running_denom < denom {
+            running_denom += 1;
+            continue;
+        }
+
+        fractions.push((1, running_denom));
+
+        let new_denom = lcm(denom, running_denom);
+        let new_num = (new_denom / denom) * num - new_denom / running_denom;
+
+        num = new_num;
+        denom = new_denom;
+
+        running_denom += 1;
+    }
+    if num >= 1 {
+        fractions.push((num, denom));
+    }
+
+    fractions
+        .iter()
+        .map(format_fraction)
+        .reduce(|acc, frac| acc + ", " + &frac)
+        .unwrap()
+}

README.md

@@ -74,6 +74,7 @@
 - [Perimeter of squares in a rectangle](https://www.codewars.com/kata/559a28007caad2ac4e000083) - [solution](5kyu/perimeter_of_squares_in_a_rectangle)
 - [My smallest code interpreter (aka Brainf**k)](https://www.codewars.com/kata/526156943dfe7ce06200063e) - [solution](5kyu/my_smallest_code_interpreter_bf)
 - [Count IP Addresses](https://www.codewars.com/kata/526989a41034285187000de4) - [solution](5kyu/count_ip_addresses)
+- [Some Egyptian fractions](https://www.codewars.com/kata/54f8693ea58bce689100065f) - [solution](5kyu/some_egyptians_fractions)
 
 ### C