Math.Combinat.Trees.Nary

N-ary trees.

Regular trees

ternaryTrees :: Int -> [Tree ()]

Ternary trees on n nodes (synonym for regularNaryTrees 3)

regularNaryTrees

Arguments

:: Int

degree = number of children of each node

-> Int

number of nodes

-> [Tree ()]

regularNaryTrees d n returns the list of (rooted) trees on n nodes where each node has exactly d children. Note that the leaves do not count in n. Naive algorithm.

semiRegularTrees

Arguments

:: [Int]

set of allowed number of children

-> Int

number of nodes

-> [Tree ()]

All trees on n nodes where the number of children of all nodes is in element of the given set. Example:

autoTabulate RowMajor (Right 5) $ map asciiTreeVertical 
                                $ map labelNChildrenTree_ 
                                $ semiRegularTrees [2,3] 2

[ length $ semiRegularTrees [2,3] n | n<-[0..] ] == [1,2,10,66,498,4066,34970,312066,2862562,26824386,...]

The latter sequence is A027307 in OEIS: https://oeis.org/A027307

Remark: clearly, we have

semiRegularTrees [d] n == regularNaryTrees d n

countTernaryTrees :: Integral a => a -> Integer

# = \frac {1} {(2n+1} \binom {3n} {n}

countRegularNaryTrees :: (Integral a, Integral b) => a -> b -> Integer

We have

length (regularNaryTrees d n) == countRegularNaryTrees d n == \frac {1} {(d-1)n+1} \binom {dn} {n} 

"derivation trees"

derivTrees :: [Int] -> [Tree ()]

Computes the set of equivalence classes of rooted trees (in the sense that the leaves of a node are unordered) with n = length ks leaves where the set of heights of the leaves matches the given set of numbers. The height is defined as the number of edges from the leaf to the root.

TODO: better name?

ASCII drawings

asciiTreeVertical_ :: Tree a -> ASCII

Vertical ASCII drawing of a tree, without labels. Example:

autoTabulate RowMajor (Right 5) $ map asciiTreeVertical_ $ regularNaryTrees 2 4 

Nodes are denoted by @, leaves by *.

asciiTreeVertical :: Show a => Tree a -> ASCII

Prints all labels. Example:

asciiTreeVertical $ addUniqueLabelsTree_ $ (regularNaryTrees 3 9) !! 666

Nodes are denoted by (label), leaves by label.

asciiTreeVerticalLeavesOnly :: Show a => Tree a -> ASCII

Prints the labels for the leaves, but not for the nodes.

Graphviz drawing

type Dot = String

graphvizDotTree

Arguments

:: Show a

=> Bool

reverse the direction of the arrow

-> String

name of the graph

-> Tree a

-> Dot

Generates graphviz .dot file from a tree. The first argument is the name of the graph.

graphvizDotForest

Arguments

:: Show a

=> Bool

make the individual trees clustered subgraphs

-> Bool

reverse the direction of the arrows

-> String

name of the graph

-> Forest a

-> Dot

Generates graphviz .dot file from a forest. The first argument tells whether to make the individual trees clustered subgraphs; the second is the name of the graph.

Classifying nodes

classifyTreeNode :: Tree a -> Either a a

Left is leaf, Right is node

isTreeLeaf :: Tree a -> Maybe a

isTreeNode :: Tree a -> Maybe a

isTreeLeaf_ :: Tree a -> Bool

isTreeNode_ :: Tree a -> Bool

treeNodeNumberOfChildren :: Tree a -> Int

Counting nodes

countTreeNodes :: Tree a -> Int

countTreeLeaves :: Tree a -> Int

countTreeLabelsWith :: (a -> Bool) -> Tree a -> Int

countTreeNodesWith :: (Tree a -> Bool) -> Tree a -> Int

Left and right spines

leftSpine :: Tree a -> ([a], a)

The leftmost spine (the second element of the pair is the leaf node)

leftSpine_ :: Tree a -> [a]

The leftmost spine without the leaf node

rightSpine :: Tree a -> ([a], a)

rightSpine_ :: Tree a -> [a]

leftSpineLength :: Tree a -> Int

The length (number of edges) on the left spine

leftSpineLength tree == length (leftSpine_ tree)

rightSpineLength :: Tree a -> Int

Unique labels

addUniqueLabelsTree :: Tree a -> Tree (a, Int)

Adds unique labels to the nodes (including leaves) of a Tree.

addUniqueLabelsForest :: Forest a -> Forest (a, Int)

Adds unique labels to the nodes (including leaves) of a Forest

addUniqueLabelsTree_ :: Tree a -> Tree Int

addUniqueLabelsForest_ :: Forest a -> Forest Int

Labelling by depth

labelDepthTree :: Tree a -> Tree (a, Int)

Attaches the depth to each node. The depth of the root is 0.

labelDepthForest :: Forest a -> Forest (a, Int)

labelDepthTree_ :: Tree a -> Tree Int

labelDepthForest_ :: Forest a -> Forest Int

Labelling by number of children

labelNChildrenTree :: Tree a -> Tree (a, Int)

Attaches the number of children to each node.

labelNChildrenForest :: Forest a -> Forest (a, Int)

labelNChildrenTree_ :: Tree a -> Tree Int

labelNChildrenForest_ :: Forest a -> Forest Int