docs: fix bugs in pseudocode

Author: danielzting

levels/cycle_sort.gd

@@ -10,8 +10,7 @@ demonstration, in the actual level, swaps are used instead.
 
 This results in a quadratic runtime but gives it the special property
 of being optimal in the number of writes to the array. This makes cycle
-sort useful in storage types where writes are very expensive or reduce
-its lifespan.
+sort useful in situations where writes are very expensive.
 
 
 If the highlighted element is less than the element below the blue
@@ -25,13 +24,17 @@ const CODE = """
 def cycle_sort(a):
     for i in range(len(a)):
         while True:
-            position = 0
-            for j in a:
-                if a[j] > a[i]:
-                    position += 1
-            if i == position:
+            less = equal = 0
+            for element in a:
+                if element < a[i]:
+                    less += 1
+                elif element == a[i]:
+                    equal += 1
+            if less <= i and i < less + equal:
                 break
-            a.swap(i, position)
+            while a[i] == a[less]:
+                less += 1
+            a.swap(i, less)
 """
 const ACTIONS = {
     "SMALLER": "Left",

levels/merge_sort.gd

@@ -26,13 +26,15 @@ def merge_sort(a):
             i = begin
             j = begin + size
             while len(merged) != size * 2:
-                if i >= begin + size or a[j] < a[i]:
-                    merged.append(a[j])
-                    j += 1
+                if i >= begin + size:
+                    merged += a[j:begin + size * 2]
+                elif j >= begin + size * 2:
+                    merged += a[i:begin + size]
+                elif a[i] < a[j]:
+                    merged.append(a[i++])
                 else:
-                    merged.append(a[i])
-                    i += 1
-            a[begin:begin + size] = merged
+                    merged.append(a[j++])
+            a[begin:begin + size * 2] = merged
         size *= 2
 """
 const ACTIONS = {

levels/quick_sort.gd

@@ -23,10 +23,9 @@ extends ComparisonSort
 const CODE = """
 def quicksort(array, low=0, high=len(a) - 1):
     if low < high:
-        pivot = a[high]
         pointer = low
         for i in range(low, high):
-            if a[i] < pivot:
+            if a[i] < a[high]:
                 a.swap(i, pointer)
                 pointer += 1
         a.swap(pointer, high)

levels/selection_sort.gd

@@ -22,7 +22,7 @@ const CODE = """
 def selection_sort(a):
     for i in range(len(a)):
         smallest = i
-        for j in range(i, len(a)):
+        for j in range(i + 1, len(a)):
             if a[j] < a[smallest]:
                 smallest = j
         a.swap(i, smallest)

levels/shell_sort.gd

@@ -27,7 +27,7 @@ def shell_sort(a):
         for i in range(gap):
             for j in range(i, len(a) - gap, gap):
                 k = j
-                while k > gap and a[k - gap] > a[k]:
+                while k > i and a[k - gap] > a[k]:
                     a.swap(k - gap, k)
                     k -= gap
 """

scripts/levels.gd

@@ -48,7 +48,7 @@ func _reload():
     _restart()
     _load_scores(_level)
     $NamesContainer/Names/Current.text = _level.NAME
-    $Level/Left/Code.text = _level.DESCRIPTION + "\n" + _level.CODE
+    $Level/Left/Code.text = _level.DESCRIPTION + "\n\n" + _level.CODE.strip_edges()
     $Level/Right/Info/ControlsContainer/Controls.text = _level.CONTROLS
 
 func _restart():