chore(Python): shell sort algorithm (#331)

algorithms/Python/README.md

@@ -30,6 +30,7 @@
 5. [Selection Sort](sorting/selection_sort.py)
 6. [Heap Sort](sorting/heap-sort.py)
 7. [Radix Sort](sorting/radix-sort.py)
+8. [Shell Sort](sorting/shell-sort.py)
  
 ## Strings
 1. [Is Good Str](strings/is_good_str.py)

algorithms/Python/sorting/shell-sort.py

@@ -0,0 +1,33 @@
+def shellSort(input_list):
+    
+    gap = len(input_list) // 2
+    while gap > 0:
+
+        for i in range(gap, len(input_list)):
+            temp = input_list[i]
+            j = i
+# Sort the sub list for this gap
+
+            while j >= gap and input_list[j - gap] > temp:
+                input_list[j] = input_list[j - gap]
+                j = j-gap
+            input_list[j] = temp
+
+# Reduce the gap for the next element
+
+        gap = gap//2
+
+list = [19,2,31,45,30,11,121,27]
+
+shellSort(list)
+print(list)
+
+
+
+#Time Complexity
+
+#Worst Case Complexity: less than or equal to O(n2) Worst case complexity for shell sort is always less than or equal to O(n2) . ...
+
+#Best Case Complexity: O(n*log n) ...
+
+#Average Case Complexity: O(n*log n)#