Data commit

Task/Sorting-Algorithms-Circle-Sort/Python/sorting-algorithms-circle-sort.py

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+#python3
+#tests: expect no output.
+#doctest with  python3 -m doctest thisfile.py
+#additional tests:  python3 thisfile.py
+
+def circle_sort_backend(A:list, L:int, R:int)->'sort A in place, returning the number of swaps':
+    '''
+        >>> L = [3, 2, 8, 28, 2,]
+        >>> circle_sort(L)
+        3
+        >>> print(L)
+        [2, 2, 3, 8, 28]
+        >>> L = [3, 2, 8, 28,]
+        >>> circle_sort(L)
+        1
+        >>> print(L)
+        [2, 3, 8, 28]
+    '''
+    n = R-L
+    if n < 2:
+        return 0
+    swaps = 0
+    m = n//2
+    for i in range(m):
+        if A[R-(i+1)] < A[L+i]:
+            (A[R-(i+1)], A[L+i],) = (A[L+i], A[R-(i+1)],)
+            swaps += 1
+    if (n & 1) and (A[L+m] < A[L+m-1]):
+        (A[L+m-1], A[L+m],) = (A[L+m], A[L+m-1],)
+        swaps += 1
+    return swaps + circle_sort_backend(A, L, L+m) + circle_sort_backend(A, L+m, R)
+
+def circle_sort(L:list)->'sort A in place, returning the number of swaps':
+    swaps = 0
+    s = 1
+    while s:
+        s = circle_sort_backend(L, 0, len(L))
+        swaps += s
+    return swaps
+
+# more tests!
+if __name__ == '__main__':
+    from random import shuffle
+    for i in range(309):
+        L = list(range(i))
+        M = L[:]
+        shuffle(L)
+        N = L[:]
+        circle_sort(L)
+        if L != M:
+            print(len(L))
+            print(N)
+            print(L)