075 Singular integer right triangles.sf

#!/usr/bin/ruby

# Author: Trizen
# Date: 21 March 2023
# https://github.com/trizen

# https://projecteuler.net/problem=75

# Runtime: 2 minutes, 33 seconds

func count_singular_integer_right_triangles(limit) {

    var table = Bag()

    for k in (1 .. idiv(limit, 2)) {
        k*k -> sum_of_squares.each_2d {|a,b|
            if (a > 0) {
                var p = a+b+k
                if (p <= limit) {
                    table << p
                }
            }
        }
    }

    table.values.count_by { .is_one }
}

assert_eq(count_singular_integer_right_triangles(48), 6)
assert_eq(count_singular_integer_right_triangles(120), 13)
assert_eq(count_singular_integer_right_triangles(1200), 129)

say count_singular_integer_right_triangles(1_500_000)