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Merged
merged 7 commits into from
Feb 26, 2025
Merged

Add utility functions to traverse trees to find minimum, maximum node and the keys adjacent to a node #13

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9d0a0bc
Add utility functions to traverse trees to find minimum, maximum node…
souma4 Feb 23, 2025
f05f43f
updating abovebelow to prevnext to be more generally descriptive. Als…
souma4 Feb 24, 2025
8773672
inlined prevnext with nothing input, and edited comments to meet style.
souma4 Feb 24, 2025
2ce4f40
added @inferred check for BT.prevnext methods. I chose to set Allowed…
souma4 Feb 24, 2025
c1ac4c0
switched inferred checks for prevnext to index into results rather th…
souma4 Feb 25, 2025
da7f4e8
removed test typo and added docstrings for new utility functions
souma4 Feb 26, 2025
1e9a292
Updated docstrings to match style and squashed commits from that proc…
souma4 Feb 26, 2025
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57 changes: 57 additions & 0 deletions src/binarytree.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -143,3 +143,60 @@ function _printkeyvalue(io::IO, node::BinaryNode)
show(ioctx, val)
end
end

# -----------
# UTILITIES
# -----------

minnode(tree::BinaryTree) = minnode(root(tree))

function minnode(node::BinaryNode)
leftnode = left(node)
isnothing(leftnode) ? node : minnode(leftnode)
end

minnode(node::Nothing) = nothing

maxnode(tree::BinaryTree) = maxnode(root(tree))

function maxnode(node::BinaryNode)
rightnode = right(node)
isnothing(rightnode) ? node : maxnode(rightnode)
end

maxnode(node::Nothing) = nothing

function prevnext(tree::BinaryTree, k)
prev, next = nothing, nothing
current = root(tree)
# traverse from the root to the target node, updating candidates
while !isnothing(current) && key(current) != k
if k < key(current)
# current is a potential next (successor)
next = current
current = left(current)
else # k > key(current)
# current is a potential previous (predecessor)
prev = current
current = right(current)
end
end

# if the node wasn't found, return the best candidate values
if isnothing(current)
return (prev, next)
end

# if there is a left subtree, the true previous (predecessor) is the maximum in that subtree
if !isnothing(left(current))
prev = maxnode(left(current))
end
# similarly, if there is a right subtree, the true next (successor) is the minimum in that subtree
if !isnothing(right(current))
next = minnode(right(current))
end

(prev, next)
end

prevnext(tree::BinaryTree, k::Nothing) = (nothing, nothing)
43 changes: 42 additions & 1 deletion test/runtests.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -93,7 +93,7 @@ const BT = BinaryTrees
BT.insert!(tree, 2, 20)
BT.insert!(tree, 1, 10)
BT.insert!(tree, 3, 30)
# deleting a key that does not exist
# deleting a key that does not exist
# does not change the tree
BT.delete!(tree, 4)
@test tree === tree
Expand Down Expand Up @@ -219,11 +219,34 @@ const BT = BinaryTrees
@test BT.value(BT.search(tree, (0, 0, 1))) == 1
@test BT.value(BT.search(tree, (1, 0, 0))) == 3

# traversal algorithms
tree = AVLTree{Int,Float64}()
BT.insert!(tree, 0, 5)
BT.insert!(tree, 1, 6)
BT.insert!(tree, 2, 8)
BT.insert!(tree, 3, 10)
BT.insert!(tree, 4, 20)
BT.insert!(tree, 5, 30)
BT.insert!(tree, 6, 40)
@test BT.key(BT.minnode(tree)) == 0
@test BT.key(BT.maxnode(tree)) == 6
@test BT.prevnext(tree, 0)[1] == nothing
@test BT.key.(BT.prevnext(tree, 2)) == (1, 3)
@test BT.key.(BT.prevnext(tree, 5)) == (4, 6)
@test BT.prevnext(tree, nothing) == (nothing, nothing)

# type stability
tree = AVLTree{Int,Int}()
@inferred BT.insert!(tree, 2, 20)
@inferred BT.insert!(tree, 1, 10)
@inferred BT.insert!(tree, 3, 30)
@inferred Nothing BT.minnode(tree)
@inferred Nothing BT.maxnode(tree)
@inferred Tuple{Union{BT.AVLNode,Nothing},Union{BT.AVLNode,Nothing}} BT.prevnext(
tree,
2
)
@inferred BT.prevnext(tree, nothing)
@inferred Nothing BT.search(tree, 2)
@inferred Nothing BT.search(tree, 1)
@inferred Nothing BT.search(tree, 3)
Expand All @@ -234,6 +257,12 @@ const BT = BinaryTrees
@inferred BT.insert!(tree, 2)
@inferred BT.insert!(tree, 1)
@inferred BT.insert!(tree, 3)
@inferred Nothing BT.minnode(tree)
@inferred Nothing BT.maxnode(tree)
@inferred Tuple{Union{BT.AVLNode,Nothing},Union{BT.AVLNode,Nothing}} BT.prevnext(
tree,
2
)
@inferred Nothing BT.search(tree, 2)
@inferred Nothing BT.search(tree, 1)
@inferred Nothing BT.search(tree, 3)
Expand All @@ -244,6 +273,12 @@ const BT = BinaryTrees
@inferred BT.insert!(tree, "key2", 2)
@inferred BT.insert!(tree, "key1", 1)
@inferred BT.insert!(tree, "key3", 3)
@inferred Nothing BT.minnode(tree)
@inferred Nothing BT.maxnode(tree)
@inferred Tuple{Union{BT.AVLNode,Nothing},Union{BT.AVLNode,Nothing}} BT.prevnext(
tree,
"key2"
)
@inferred Nothing BT.search(tree, "key2")
@inferred Nothing BT.search(tree, "key1")
@inferred Nothing BT.search(tree, "key3")
Expand All @@ -254,6 +289,12 @@ const BT = BinaryTrees
@inferred BT.insert!(tree, (0, 1, 0), 2)
@inferred BT.insert!(tree, (0, 0, 1), 1)
@inferred BT.insert!(tree, (1, 0, 0), 3)
@inferred Nothing BT.minnode(tree)
@inferred Nothing BT.maxnode(tree)
@inferred Tuple{Union{BT.AVLNode,Nothing},Union{BT.AVLNode,Nothing}} BT.prevnext(
tree,
(0, 1, 0)
)
@inferred Nothing BT.search(tree, (0, 1, 0))
@inferred Nothing BT.search(tree, (0, 0, 1))
@inferred Nothing BT.search(tree, (1, 0, 0))
Expand Down