tasks a-s

Task/Self-referential-sequence/Icon/self-referential-sequence-1.icon

@@ -0,0 +1,38 @@
+link printf
+
+procedure main()
+every L := !longestselfrefseq(1000000) do
+   every printf(" %i : %i\n",i := 1 to *L,L[i])
+end
+
+
+procedure longestselfrefseq(N)    #: find longest sequences from 1 to N
+
+mlen := 0
+every L := selfrefseq(n := 1 to N) do {
+   if mlen <:= *L then
+      ML := [L]
+   else if mlen = *L then
+      put(ML,L)
+   }
+
+return ML
+end
+
+procedure selfrefseq(n) #: return list of sequence oeis:A036058 for seed n
+S := set()
+L := []
+every p := seq(1) do
+   if member(S,n) then return L   # ends at a repeat
+   else {
+      insert(S,n)
+      put(L,n)
+      n := nextselfrefseq(n)
+      }
+end
+
+procedure nextselfrefseq(n)  #: return next element of sequence oeis:A036058
+every (Counts := table(0))[integer(!n)] +:= 1              # count digits
+every (n := "") ||:= (0 < Counts[i := 9 to 0 by -1]) || i  # assemble counts
+return integer(n)
+end