feat: add shell sort and selection sort in Python (doocs#814)

Author: tlei995

basic/sorting/SelectionSort/SelectionSort.py

@@ -0,0 +1,13 @@
+def selectionSort(arr):
+    n = len(arr)
+    for i in range(n - 1):
+        min_index = i
+        for j in range(i + 1, n):
+            if arr[j] < arr[min_index]:
+                min_index = j
+        arr[min_index], arr[i] = arr[i], arr[min_index]
+
+
+arr = [26, 11, 99, 33, 69, 77, 55, 56, 67]
+selectionSort(arr)
+print(arr)

basic/sorting/ShellSort/ShellSort.py

@@ -0,0 +1,17 @@
+def shellSort(arr):
+    n = len(arr)
+    gap = int(n / 2)
+    while gap > 0:
+        for i in range(gap, n):
+            temp = arr[i]
+            j = i
+            while j >= gap and arr[j - gap] > temp:
+                arr[j] = arr[j - gap]
+                j -= gap
+            arr[j] = temp
+        gap = int(gap / 2)
+
+
+arr = [12, 34, 54, 2, 3]
+shellSort(arr)
+print(arr)