Double sort (Added with required updates) (#1399)

* Added with required updates

* Updated

* required updates

* Update double_sort.py

* Update double_sort.py

Author: ayush246

sorts/double_sort.py

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+def double_sort(lst): 
+    """this sorting algorithm sorts an array using the principle of bubble sort , 
+    but does it both from left to right and right to left , 
+    hence i decided to call it "double sort"
+    :param collection: mutable ordered sequence of elements
+    :return: the same collection in ascending order
+    Examples:
+    >>> double_sort([-1 ,-2 ,-3 ,-4 ,-5 ,-6 ,-7])
+    [-7, -6, -5, -4, -3, -2, -1]
+    >>> double_sort([])
+    []
+    >>> double_sort([-1 ,-2 ,-3 ,-4 ,-5 ,-6])
+    [-6, -5, -4, -3, -2, -1]
+    >>> double_sort([-3, 10, 16, -42, 29]) == sorted([-3, 10, 16, -42, 29])
+    True
+    """
+    no_of_elements=len(lst)
+    for i in range(0,int(((no_of_elements-1)/2)+1)): # we dont need to traverse to end of list as
+        for j in range(0,no_of_elements-1):
+            if (lst[j+1]<lst[j]): # applying bubble sort algorithm from left to right (or forwards)
+                temp=lst[j+1]
+                lst[j+1]=lst[j]
+                lst[j]=temp
+            if (lst[no_of_elements-1-j]<lst[no_of_elements-2-j]): # applying bubble sort algorithm from right to left (or backwards)
+                temp=lst[no_of_elements-1-j]
+                lst[no_of_elements-1-j]=lst[no_of_elements-2-j]
+                lst[no_of_elements-2-j]=temp
+    return lst
+if __name__ == "__main__":
+    print("enter the list to be sorted")
+    lst = [int(x) for x in input().split()] # inputing elements of the list in one line
+    sorted_lst=double_sort(lst)
+    print("the sorted list is")
+    print(sorted_lst)