fix: make cycle sort work with duplicate elements

Some logic in cycle sort assumed a random permutation of elements.

Author: danielzting

levels/cycle_sort.gd

@@ -54,8 +54,11 @@ func next(action):
             return emit_signal("mistake")
     _index += 1
     if _index == array.size:
+        # Skip over duplicates to avoid infinite cycling
+        while _smaller != _pointer and array.at(_pointer) == array.at(_smaller):
+            _smaller += 1
         array.swap(_pointer, _smaller)
-        while array.at(_pointer) == _pointer + 1:
+        while array.is_in_place(_pointer):
             _pointer += 1
             if _pointer == array.size:
                 return emit_signal("done")

models/array_model.gd

@@ -87,6 +87,17 @@ func sort(i, j):
     _array = front + sorted + back
     emit_signal("sorted", i, j)
 
+func is_in_place(i):
+    """Check if the element at index i is in its correct place."""
+    var less = 0
+    var equal = 0
+    for element in _array:
+        if element < _array[i]:
+            less += 1
+        elif element == _array[i]:
+            equal += 1
+    return less <= i and i < less + equal
+
 func get_size():
     return _array.size()