September Morn Update

Task/Self-referential-sequence/Julia/self-referential-sequence.julia

@@ -0,0 +1,61 @@
+const seen = Dict{Vector{Char}, Vector{Char}}()
+
+function findnextterm(prevterm)
+    counts = Dict{Char, Int}()
+    reversed = Vector{Char}()
+    for c in prevterm
+        if !haskey(counts, c)
+            counts[c] = 0
+        end
+        counts[c] += 1
+    end
+    for c in sort(collect(keys(counts)))
+        if counts[c] > 0
+            push!(reversed, c)
+            if counts[c] == 10
+                push!(reversed, '0'); push!(reversed, '1')
+            else
+                push!(reversed, Char(UInt8(counts[c]) + UInt8('0')))
+            end
+        end
+    end
+    reverse(reversed)
+end
+
+function findsequence(seedterm)
+    term = seedterm
+    sequence = Vector{Vector{Char}}()
+    while !(term in sequence)
+        push!(sequence, term)
+        if !haskey(seen, term)
+            nextterm = findnextterm(term)
+            seen[term] = nextterm
+        end
+        term = seen[term]
+    end
+    return sequence
+end
+
+function selfseq(maxseed)
+    maxseqlen = -1
+    maxsequences = Vector{Pair{Int, Vector{Char}}}()
+    for i in 1:maxseed
+        seq = findsequence([s[1] for s in split(string(i), "")])
+        seqlen = length(seq)
+        if seqlen > maxseqlen
+            maxsequences = [Pair(i, seq)]
+            maxseqlen = seqlen
+        elseif seqlen == maxseqlen
+            push!(maxsequences, Pair(i, seq))
+        end
+    end
+    println("The longest sequence length is $maxseqlen.")
+    for p in maxsequences
+        println("\n Seed: $(p[1])")
+        for seq in p[2]
+            println("     ", join(seq, ""))
+        end
+    end
+end
+
+selfseq(1000000)