Added strand sort (TheAlgorithms#1982)

* Added strand sort

* Review changes

* Remove boilerplate code

* Fixed flake error: E252

* Added missing return type hint

Author: l3str4nge

sorts/strand_sort.py

@@ -0,0 +1,51 @@
+import operator
+
+
+def strand_sort(arr: list, reverse: bool = False, solution: list = None) -> list:
+    """
+    Strand sort implementation
+    source: https://en.wikipedia.org/wiki/Strand_sort
+
+    :param arr: Unordered input list
+    :param reverse: Descent ordering flag
+    :param solution: Ordered items container
+
+    Examples:
+    >>> strand_sort([4, 2, 5, 3, 0, 1])
+    [0, 1, 2, 3, 4, 5]
+
+    >>> strand_sort([4, 2, 5, 3, 0, 1], reverse=True)
+    [5, 4, 3, 2, 1, 0]
+    """
+    _operator = operator.lt if reverse else operator.gt
+    solution = solution or []
+
+    if not arr:
+        return solution
+
+    sublist = [arr.pop(0)]
+    for i, item in enumerate(arr):
+        if _operator(item, sublist[-1]):
+            sublist.append(item)
+            arr.pop(i)
+
+    #  merging sublist into solution list
+    if not solution:
+        solution.extend(sublist)
+    else:
+        while sublist:
+            item = sublist.pop(0)
+            for i, xx in enumerate(solution):
+                if not _operator(item, xx):
+                    solution.insert(i, item)
+                    break
+            else:
+                solution.append(item)
+
+    strand_sort(arr, reverse, solution)
+    return solution
+
+
+if __name__ == "__main__":
+    assert strand_sort([4, 3, 5, 1, 2]) == [1, 2, 3, 4, 5]
+    assert strand_sort([4, 3, 5, 1, 2], reverse=True) == [5, 4, 3, 2, 1]