feat: add selection sort

A modified version of selection sort is now available to play. To save
development time, instead of just keeping track of the smallest element,
it actually swaps every time it encounters a new low. This will likely
have to be changed in a future release as it's pretty confusing.

Author: danielzting

levels/selection_sort.gd

@@ -0,0 +1,33 @@
+extends ComparisonSort
+class_name SelectionSort
+
+const TITLE = "SELECTION SORT"
+const ABOUT = """Selection sort incrementally builds a sorted array by
+repeatedly looking for the smallest element and swapping it onto the
+end of the sorted portion of the array, which initially starts with size
+zero but grows after each round. It is faster than an unoptimized bubble
+sort but slower than insertion sort."""
+var base = 0
+var index = base + 1
+
+func _init(array).(array):
+    pass
+
+func check(action):
+    if array.get(base) > array.get(index):
+        return action == "swap"
+    else:
+        return action == "no_swap"
+
+func next():
+    if array.get(base) > array.get(index):
+        array.swap(base, index)
+    index += 1
+    if index == array.size:
+        base += 1
+        index = base + 1
+    if base == array.size - 1:
+        emit_signal("done")
+
+func emphasized(i):
+    return i == index or i == base

project.godot

@@ -38,14 +38,20 @@ _global_script_classes=[ {
 "class": "InsertionSort",
 "language": "GDScript",
 "path": "res://levels/insertion_sort.gd"
+}, {
+"base": "ComparisonSort",
+"class": "SelectionSort",
+"language": "GDScript",
+"path": "res://levels/selection_sort.gd"
 } ]
 _global_script_class_icons={
 "ArrayModel": "",
 "ArrayView": "",
 "BogoSort": "",
 "BubbleSort": "",
 "ComparisonSort": "",
-"InsertionSort": ""
+"InsertionSort": "",
+"SelectionSort": ""
 }
 
 [application]

scripts/levels.gd

@@ -3,6 +3,7 @@ extends HBoxContainer
 var levels = [
     BubbleSort,
     InsertionSort,
+    SelectionSort,
 ]
 var level: ComparisonSort