June 2018 Update

Task/Self-describing-numbers/Red/self-describing-numbers.red

@@ -0,0 +1,30 @@
+Red []
+
+;;-------------------------------------
+count-dig: func ["count occurence of digit in number"
+;;-------------------------------------
+  s [string!] "number as string"
+  sdig [char!] "search number as char"
+][
+cnt: #"0" ;; counter as char for performance optimization
+
+while [s: find/tail s sdig][cnt: cnt + 1]
+return cnt
+]
+
+;;-------------------------------------
+isSDN?: func ["test if number is self describing number"
+  s [string!] "number to test as string "
+  ][
+;;-------------------------------------
+
+ind: #"0" ;; use digit as char for performance optimization
+
+foreach ele s [
+  if ele <> count-dig s ind [return false]
+  ind: ind + 1
+]
+return true
+]
+
+repeat i 4000000 [  if isSDN? to-string i [print i] ]