Data commit

Task/Weird-numbers/Crystal/weird-numbers.crystal

@@ -0,0 +1,91 @@
+def divisors(n : Int32) : Array(Int32)
+  divs = [1]
+  divs2 = [] of Int32
+
+  i = 2
+  while i * i < n
+    if n % i == 0
+      j = n // i
+      divs << i
+      divs2 << j if i != j
+    end
+
+    i += 1
+  end
+
+  i = divs.size - 1
+
+  # TODO: Use reverse
+  while i >= 0
+    divs2 << divs[i]
+    i -= 1
+  end
+
+  divs2
+end
+
+def abundant(n : Int32, divs : Array(Int32)) : Bool
+  divs.sum > n
+end
+
+def semiperfect(n : Int32, divs : Array(Int32)) : Bool
+  if divs.size > 0
+    h = divs[0]
+    t = divs[1..]
+
+    return n < h ? semiperfect(n, t) : n == h || semiperfect(n - h, t) || semiperfect(n, t)
+  end
+
+  return false
+end
+
+def sieve(limit : Int32) : Array(Bool)
+  # false denotes abundant and not semi-perfect.
+  # Only interested in even numbers >= 2
+
+  w = Array(Bool).new(limit, false) # An array filled with 'false'
+
+  i = 2
+  while i < limit
+    if !w[i]
+      divs = divisors i
+
+      if !abundant(i, divs)
+        w[i] = true
+      elsif semiperfect(i, divs)
+        j = i
+        while j < limit
+          w[j] = true
+          j += i
+        end
+      end
+    end
+
+    i += 2
+  end
+
+  w
+end
+
+def main
+  w = sieve 17000
+  count = 0
+  max = 25
+
+  print "The first 25 weird numbers are: "
+
+  n = 2
+  while count < max
+    if !w[n]
+      print "#{n} "
+      count += 1
+    end
+
+    n += 2
+  end
+
+  puts "\n"
+end
+
+require "benchmark"
+puts Benchmark.measure { main }