reversed method applied in DODA (#211)

Co-authored-by: Harsheet-saxena <harshsaxena1999@gmail.com>

Author: HarsheetKakar

pydatastructs/linear_data_structures/arrays.py

@@ -255,6 +255,10 @@ def delete(self, idx):
     def size(self):
         return self._size
 
+    def __reversed__(self):
+        for i in range(self._last_pos_filled, -1, -1):
+            yield self._data[i]
+
 class ArrayForTrees(DynamicOneDimensionalArray):
     """
     Utility dynamic array for storing nodes of a tree.

pydatastructs/linear_data_structures/tests/test_arrays.py

@@ -37,3 +37,11 @@ def test_DynamicOneDimensionalArray():
     assert A.size == 3
     A.fill(4)
     assert A._data == [4, 4, 4]
+    b = DynamicOneDimensionalArray(int, 0)
+    b.append(1)
+    b.append(2)
+    b.append(3)
+    b.append(4)
+    b.append(5)
+    assert b._data == [1, 2, 3, 4, 5, None, None]
+    assert list(reversed(b)) == [5, 4, 3, 2, 1]