feat: add shell sort

To make it easier to focus on the current gap subarray in shell sort,
dimmed elements are now even darker (opacity decreased 4x from 0.5 ->
0.125).

Author: danielzting

levels/shell_sort.gd

@@ -0,0 +1,61 @@
+class_name ShellSort
+extends ComparisonSort
+
+const NAME = "SHELL SORT"
+const ABOUT = """
+Shell sort is a variation of insertion sort that sorts arrays separated
+by gaps.
+"""
+const CONTROLS = """
+Hit LEFT ARROW to swap the two highlighted elements as long as they are
+out of order. When this is no longer the case, hit RIGHT ARROW to
+advance.
+"""
+
+const ACTIONS = {
+    "SWAP": "Left",
+    "CONTINUE": "Right",
+}
+var _gap = array.size / 2
+var _begin = 0 # First element of subarray
+var _end = _gap # End of the sorted subarray
+var _index = _gap # Position of element currently being inserted
+
+func _init(array).(array):
+    pass
+
+func next(action):
+    if array.at(_index - _gap) > array.at(_index):
+        if action != null and action != ACTIONS.SWAP:
+            return emit_signal("mistake")
+        array.swap(_index - _gap, _index)
+        _index -= _gap
+        if _index - _gap < 0:
+            _grow()
+    else:
+        if action != null and action != ACTIONS.CONTINUE:
+            return emit_signal("mistake")
+        _grow()
+
+func get_effect(i):
+    if i == _index - _gap or i == _index:
+        return EFFECTS.HIGHLIGHTED
+    if (i - _begin) % _gap != 0:
+        return EFFECTS.DIMMED
+    return EFFECTS.NONE
+
+func get_pointer():
+    return _end
+
+func _grow():
+    _end += _gap
+    _index = _end
+    if _end >= array.size:
+        _begin += 1
+        if _begin >= _gap:
+            _gap /= 2
+            if _gap == 0:
+                emit_signal("done")
+            _begin = 0
+        _end = _gap + _begin
+        _index = _gap + _begin

project.godot

@@ -68,6 +68,11 @@ _global_script_classes=[ {
 "class": "SelectionSort",
 "language": "GDScript",
 "path": "res://levels/selection_sort.gd"
+}, {
+"base": "ComparisonSort",
+"class": "ShellSort",
+"language": "GDScript",
+"path": "res://levels/shell_sort.gd"
 } ]
 _global_script_class_icons={
 "ArrayModel": "",
@@ -81,7 +86,8 @@ _global_script_class_icons={
 "MergeSort": "",
 "QuickSort": "",
 "Score": "",
-"SelectionSort": ""
+"SelectionSort": "",
+"ShellSort": ""
 }
 
 [application]

scripts/levels.gd

@@ -7,6 +7,7 @@ const LEVELS = [
     MergeSort,
     QuickSort,
     CocktailSort,
+    ShellSort,
 ]
 const MIN_WAIT = 1.0 / 32 # Should be greater than maximum frame time
 const MAX_WAIT = 4

scripts/theme.gd

@@ -5,7 +5,7 @@ Global constants relating to the GUI.
 extends Node
 
 const GREEN = Color("33ff33")
-const DARK_GREEN = Color("1b5e20")
+const DARK_GREEN = Color("072107")
 const ORANGE = Color("ffb000")
 const RED = Color("f44336")
 const BLUE = Color("2196f3")

views/array_view.gd

@@ -89,9 +89,14 @@ func _on_ArrayModel_swapped(i, j):
     _tween.start()
 
 func _draw():
-    var width = rect_size.x + MARGIN
-    var height = rect_size.y + MARGIN
+    # Prevent lines from "sticking" into border
+    var margin = preload("res://scripts/border.gd").WIDTH / 2
+    var width = rect_size.x + MARGIN - margin
+    var height = rect_size.y + MARGIN - margin
+    var start = -MARGIN + margin
+    # Vertical lines
     for i in range(-MARGIN + BOX_SIZE, width, BOX_SIZE):
-        draw_line(Vector2(i, -MARGIN), Vector2(i, height), LINE_COLOR)
+        draw_line(Vector2(i, start), Vector2(i, height - 1), LINE_COLOR)
+    # Horizontal lines
     for i in range(-MARGIN + BOX_SIZE, height, BOX_SIZE):
-        draw_line(Vector2(-MARGIN, i), Vector2(width, i), LINE_COLOR)
+        draw_line(Vector2(start, i), Vector2(width - 1, i), LINE_COLOR)