pythagorean-triple.rs

use std::collections::HashSet;

pub fn find(sum: u32) -> HashSet<[u32; 3]> {
  (2..(sum / 2))
    .map(|a| {
      let b_plus_c = sum - a;
      let b_numerator = b_plus_c.pow(2) - a.pow(2);
      let b_denominator = 2 * b_plus_c;

      let b = b_numerator / b_denominator;
      let c = b_plus_c - b;
      ([a, b, c], b_numerator % b_denominator)
    })
    .filter(|(_, remainder)| remainder == &0)
    .map(|(triplet, _)| triplet)
    .collect()
}