Tree traversal in smalltalk (#453)

Author: Neverik

contents/tree_traversal/code/smalltalk/tree_traversal.st

@@ -0,0 +1,81 @@
+Object subclass: #Node
+ instanceVariableNames: 'children data'
+ classVariableNames: ''
+ package: ''
+
+Node>>children
+ "Children getter."
+ ^ children
+
+Node>>children: newChildren
+ "Children setter."
+ children := newChildren.
+
+Node>>data
+ "Data getter"
+ ^ data
+
+Node>>data: newData
+ "Data setter"
+ data := newData.
+
+Node>>dfsRecursive
+ "Recursive depth first search."
+ Transcript show: data; cr.
+ children collect: [ :child | child dfsRecursive ]
+
+Node>>dfsRecursivePostOrder
+ "Recursive depth first search (post-order)."
+ children collect: [ :child | (child dfsRecursivePostOrder)].
+ Transcript show: data; cr.
+ 
+Node>>dfsInOrderBinaryTree
+ "Recursive depth first search on a binary tree in order."
+ children size > 2 ifTrue: [
+ Transcript show: 'This is not a binary tree!'; cr.
+ ^self.
+ ].
+ children size = 2 ifTrue: [
+ (children at: 1) dfsInOrderBinaryTree: value.
+ ].
+ Transcript show: data; cr.
+ children size >= 1 ifTrue: [
+ (children at: 0) dfsInOrderBinaryTree: value.
+ ].
+ ^self.
+
+Node>>dfsStack
+ "Depth-first search with a stack."
+ | stack top |
+ stack := Stack new.
+ stack push: self.
+ [stack size > 0] whileTrue: [
+ top := stack pop.
+Transcript show: (top data); cr.
+ top children reverseDo: [ :child |
+ stack push: child.
+ ].
+ ].
+
+Node>>bfs
+ "A breadth-first tree search using queues."
+ | queue current |
+ queue := LinkedList with: self.
+ [ queue size > 0 ] whileTrue: [
+ current := queue first.
+queue removeFirst.
+Transcript show: (current data); cr.
+current children collect: [ :child |
+ queue addLast: child
+ ].
+ ].
+
+| test |
+test := Node new: 1 children: { Node new: 2.
+ Node new: 3 children: { Node new: 4.
+ Node new: 5. } }.
+test dfsRecursive.
+test dfsRecursivePostorder.
+test dfsInOrderBinaryTree.
+test dfsStack.
+test bfs.

contents/tree_traversal/tree_traversal.md

@@ -32,6 +32,8 @@ As a note, a `node` struct is not necessary in javascript, so this is an example
 [import:4-37, lang:"php"](code/php/tree_traversal.php)
 {% sample lang="crystal" %}
 [import:1-5, lang:"crystal"](code/crystal/tree-traversal.cr)
+{% sample lang="st" %}
+[import:1-20, lang:"smalltalk"](code/smalltalk/tree_traversal.st)
 {% sample lang="go" %}
 [import:5-8, lang:"go"](code/golang/treetraversal.go)
 {% sample lang="asm-x64" %}
@@ -77,6 +79,8 @@ Because of this, the most straightforward way to traverse the tree might be recu
 [import:41-49, lang:"php"](code/php/tree_traversal.php)
 {% sample lang="crystal" %}
 [import:7-10, lang:"crystal"](code/crystal/tree-traversal.cr)
+{% sample lang="st" %}
+[import:22-27, lang:"smalltalk"](code/smalltalk/tree_traversal.st)
 {% sample lang="go" %}
 [import:10-15, lang:"go"](code/golang/treetraversal.go)
 {% sample lang="asm-x64" %}
@@ -131,6 +135,8 @@ Now, in this case the first element searched through is still the root of the tr
 [import:51-57, lang:"php"](code/php/tree_traversal.php)
 {% sample lang="crystal" %}
 [import:12-15, lang:"crystal"](code/crystal/tree-traversal.cr)
+{% sample lang="st" %}
+[import:29-34, lang:"smalltalk"](code/smalltalk/tree_traversal.st)
 {% sample lang="go" %}
 [import:17-22, lang:"go"](code/golang/treetraversal.go)
 {% sample lang="asm-x64" %}
@@ -180,6 +186,8 @@ In this case, the first node visited is at the bottom of the tree and moves up t
 [import:59-78, lang:"php"](code/php/tree_traversal.php)
 {% sample lang="crystal" %}
 [import:17-31, lang:"crystal"](code/crystal/tree-traversal.cr)
+{% sample lang="st" %}
+[import:36-49, lang:"smalltalk"](code/smalltalk/tree_traversal.st)
 {% sample lang="go" %}
 [import:24-38, lang:"go"](code/golang/treetraversal.go)
 {% sample lang="asm-x64" %}
@@ -238,6 +246,8 @@ In code, it looks like this:
 [import:80-91, lang:"php"](code/php/tree_traversal.php)
 {% sample lang="crystal" %}
 [import:33-41, lang:"crystal"](code/crystal/tree-traversal.cr)
+{% sample lang="st" %}
+[import:47-58, lang:"smalltalk"](code/smalltalk/tree_traversal.st)
 {% sample lang="go" %}
 [import:40-49, lang:"go"](code/golang/treetraversal.go)
 {% sample lang="asm-x64" %}
@@ -289,6 +299,8 @@ And this is exactly what Breadth-First Search (BFS) does! On top of that, it can
 [import:93-104, lang:"php"](code/php/tree_traversal.php)
 {% sample lang="crystal" %}
 [import:43-51, lang:"crystal"](code/crystal/tree-traversal.cr)
+{% sample lang="st" %}
+[import:60-71, lang:"smalltalk"](code/smalltalk/tree_traversal.st)
 {% sample lang="go" %}
 [import:51-60, lang:"go"](code/golang/treetraversal.go)
 {% sample lang="asm-x64" %}
@@ -351,6 +363,8 @@ The code snippets were taken from this [Scratch project](https://scratch.mit.edu
 [import, lang:"php"](code/php/tree_traversal.php)
 {% sample lang="crystal" %}
 [import, lang:"crystal"](code/crystal/tree-traversal.cr)
+{% sample lang="st" %}
+[import, lang:"smalltalk"](code/smalltalk/tree_traversal.st)
 {% sample lang="go" %}
 [import, lang:"go"](code/golang/treetraversal.go)
 {% sample lang="asm-x64" %}