Problem Statement

These define three classifications of positive integers based on their   proper divisors. Let   P(n)   be the sum of the proper divisors of   n   where the proper divisors are all positive divisors of   n   other than   n   itself.

6   has proper divisors of   1,   2,   and   3. 1 + 2 + 3 = 6,   so   6   is classed as a perfect number.

Calculate how many of the integers   1   to   20,000   (inclusive) are in each of the three classes. Show the results here.

Let's start with the solution:

shared void run() {

	function divisors(Integer int) => 
			if(int <= 1) then {} else (1..int / 2).filter((Integer element) => element.divides(int));
	
	function classify(Integer int) => sum {0, *divisors(int)} <=> int;
	
	value counts = (1..20k).map(classify).frequencies();
	
	print("deficient: ``counts[smaller] else "none"``");
	print("perfect:   ``counts[equal] else "none"``");
	print("abundant:  ``counts[larger] else "none"``");
}