Task: Eertree





Java: import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class Eertree {
    public static void main(String[] args) {
        List<Node> tree = eertree("eertree");
        List<String> result = subPalindromes(tree);
        System.out.println(result);
    }

    private static class Node {
        int length;
        Map<Character, Integer> edges = new HashMap<>();
        int suffix;

        public Node(int length) {
            this.length = length;
        }

        public Node(int length, Map<Character, Integer> edges, int suffix) {
            this.length = length;
            this.edges = edges != null ? edges : new HashMap<>();
            this.suffix = suffix;
        }
    }

    private static final int EVEN_ROOT = 0;
    private static final int ODD_ROOT = 1;

    private static List<Node> eertree(String s) {
        List<Node> tree = new ArrayList<>();
        tree.add(new Node(0, null, ODD_ROOT));
        tree.add(new Node(-1, null, ODD_ROOT));
        int suffix = ODD_ROOT;
        int n, k;
        for (int i = 0; i < s.length(); ++i) {
            char c = s.charAt(i);
            for (n = suffix; ; n = tree.get(n).suffix) {
                k = tree.get(n).length;
                int b = i - k - 1;
                if (b >= 0 && s.charAt(b) == c) {
                    break;
                }
            }
            if (tree.get(n).edges.containsKey(c)) {
                suffix = tree.get(n).edges.get(c);
                continue;
            }
            suffix = tree.size();
            tree.add(new Node(k + 2));
            tree.get(n).edges.put(c, suffix);
            if (tree.get(suffix).length == 1) {
                tree.get(suffix).suffix = 0;
                continue;
            }
            while (true) {
                n = tree.get(n).suffix;
                int b = i - tree.get(n).length - 1;
                if (b >= 0 && s.charAt(b) == c) {
                    break;
                }
            }
            tree.get(suffix).suffix = tree.get(n).edges.get(c);
        }
        return tree;
    }

    private static List<String> subPalindromes(List<Node> tree) {
        List<String> s = new ArrayList<>();
        subPalindromes_children(0, "", tree, s);
        for (Map.Entry<Character, Integer> cm : tree.get(1).edges.entrySet()) {
            String ct = String.valueOf(cm.getKey());
            s.add(ct);
            subPalindromes_children(cm.getValue(), ct, tree, s);
        }
        return s;
    }

    
    private static void subPalindromes_children(final int n, final String p, final List<Node> tree, List<String> s) {
        for (Map.Entry<Character, Integer> cm : tree.get(n).edges.entrySet()) {
            Character c = cm.getKey();
            Integer m = cm.getValue();
            String pl = c + p + c;
            s.add(pl);
            subPalindromes_children(m, pl, tree, s);
        }
    }
}




VB: Module Module1

    Class Node
        Public Sub New(Len As Integer)
            Length = Len
            Edges = New Dictionary(Of Char, Integer)
        End Sub

        Public Sub New(len As Integer, edg As Dictionary(Of Char, Integer), suf As Integer)
            Length = len
            Edges = If(IsNothing(edg), New Dictionary(Of Char, Integer), edg)
            Suffix = suf
        End Sub

        Property Edges As Dictionary(Of Char, Integer)
        Property Length As Integer
        Property Suffix As Integer
    End Class

    ReadOnly EVEN_ROOT As Integer = 0
    ReadOnly ODD_ROOT As Integer = 1

    Function Eertree(s As String) As List(Of Node)
        Dim tree As New List(Of Node) From {
            New Node(0, New Dictionary(Of Char, Integer), ODD_ROOT),
            New Node(-1, New Dictionary(Of Char, Integer), ODD_ROOT)
        }
        Dim suffix = ODD_ROOT
        Dim n As Integer
        Dim k As Integer

        For i = 1 To s.Length
            Dim c = s(i - 1)
            n = suffix
            While True
                k = tree(n).Length
                Dim b = i - k - 2
                If b >= 0 AndAlso s(b) = c Then
                    Exit While
                End If
                n = tree(n).Suffix
            End While
            If tree(n).Edges.ContainsKey(c) Then
                suffix = tree(n).Edges(c)
                Continue For
            End If
            suffix = tree.Count
            tree.Add(New Node(k + 2))
            tree(n).Edges(c) = suffix
            If tree(suffix).Length = 1 Then
                tree(suffix).Suffix = 0
                Continue For
            End If
            While True
                n = tree(n).Suffix
                Dim b = i - tree(n).Length - 2
                If b >= 0 AndAlso s(b) = c Then
                    Exit While
                End If
            End While
            Dim a = tree(n)
            Dim d = a.Edges(c)
            Dim e = tree(suffix)
            e.Suffix = d
        Next

        Return tree
    End Function

    Function SubPalindromes(tree As List(Of Node)) As List(Of String)
        Dim s As New List(Of String)
        Dim children As Action(Of Integer, String) = Sub(n As Integer, p As String)
                                                         For Each c In tree(n).Edges.Keys
                                                             Dim m = tree(n).Edges(c)
                                                             Dim p1 = c + p + c
                                                             s.Add(p1)
                                                             children(m, p1)
                                                         Next
                                                     End Sub
        children(0, "")
        For Each c In tree(1).Edges.Keys
            Dim m = tree(1).Edges(c)
            Dim ct = c.ToString()
            s.Add(ct)
            children(m, ct)
        Next
        Return s
    End Function

    Sub Main()
        Dim tree = Eertree("eertree")
        Dim result = SubPalindromes(tree)
        Dim listStr = String.Join(", ", result)
        Console.WriteLine("[{0}]", listStr)
    End Sub

End Module