Data commit

Task/Eertree/Julia/eertree.julia

@@ -0,0 +1,78 @@
+mutable struct Node
+    edges::Dict{Char, Node}
+    link::Union{Node, Missing}
+    sz::Int
+    Node() = new(Dict(), missing, 0)
+end
+
+sizednode(x) = (n = Node(); n.sz = x; n)
+
+function eertree(str)
+    nodes = Vector{Node}()
+    oddroot = sizednode(-1)
+    evenroot = sizednode(0)
+    oddroot.link = evenroot
+    evenroot.link = oddroot
+    S = "0"
+    maxsuffix = evenroot
+
+    function maxsuffixpal(startnode,a::Char)
+        # Traverse the suffix-palindromes of tree looking for equality with a
+        u = startnode
+        i = length(S)
+        k = u.sz
+        while u !== oddroot && S[i - k] != a
+            if u === u.link
+                throw("circular reference above oddroot")
+            end
+            u = u.link
+            k = u.sz
+        end
+        u
+    end
+
+    function addchar(a::Char)
+        Q = maxsuffixpal(maxsuffix, a)
+        creatednode = !haskey(Q.edges, a)
+        if creatednode
+            P = sizednode(Q.sz + 2)
+            push!(nodes, P)
+            if P.sz == 1
+                P.link = evenroot
+            else
+                P.link = maxsuffixpal(Q.link, a).edges[a]
+            end
+            Q.edges[a] = P            # adds edge (Q, P)
+        end
+        maxsuffix = Q.edges[a]        # P becomes the new maxsuffix
+        S *= string(a)
+        creatednode
+    end
+
+    function getsubpalindromes()
+        result = Vector{String}()
+        getsubpalindromes(oddroot, [oddroot], "", result)
+        getsubpalindromes(evenroot, [evenroot], "", result)
+        result
+    end
+
+    function getsubpalindromes(nd, nodestohere, charstohere, result)
+        for (lnkname, nd2) in nd.edges
+            getsubpalindromes(nd2, vcat(nodestohere, nd2), charstohere * lnkname, result)
+        end
+        if nd !== oddroot && nd !== evenroot
+            assembled = reverse(charstohere) *
+                (nodestohere[1] === evenroot ? charstohere : charstohere[2:end])
+            push!(result, assembled)
+        end
+    end
+
+    println("Results of processing string \"$str\":")
+    for c in str
+        addchar(c)
+    end
+    println("Number of sub-palindromes: ", length(nodes))
+    println("Sub-palindromes: ", getsubpalindromes())
+end
+
+eertree("eertree")