updated tests/README and minor chgs to binary indexed tree

README.md

@@ -1,2 +1,2 @@
 # Data Structures
-This project contains a variety of data structures implemented in python with a set of tests that achieve a near 100% code coverage.
+This project contains a variety of data structures implemented in python with a set of tests that achieves nearly 100% code coverage. Data structures implemented in this repo include: Linked list, doubly linked list, min heap, max heap, deque, binary search tree, binary indexed tree, segment tree, disjoint sets (union find), trie, LRU cache, and LFU cache.

ds/binary_indexed_tree.py

@@ -61,7 +61,7 @@ def update(self, idx: int, val: Union[int, float]) -> None:
             self.binary_idx_tree[idx - 1] += net_chg  # Apply the net change to this tree node
             idx = idx + (idx & -idx)  # Get the next parent range index
 
-    def _range_query(self, end: int) -> Union[float, int]:
+    def _prefix_sum(self, end: int) -> Union[float, int]:
         """
         Internal helper function for performing range queries. Computes the sum of all elements up through
         index end. This method is used by range_query to compute the sum of elements start:end by taking the
@@ -109,9 +109,9 @@ def range_query(self, start: int, end: int) -> Union[float, int]:
         if start == end:  # Handle special edge case when start == end, return the entry of the original arr
             return self.arr[end]
 
-        ans = self._range_query(end)  # Compute the sum up through the end index
+        ans = self._prefix_sum(end)  # Compute the sum up through the end index
         if start > 0:  # If the start is above index 0, then subtract the sum of elements through (start - 1)
-            ans -= self._range_query(start - 1)  # so that the result is the sum of arr[start:(end + 1)]
+            ans -= self._prefix_sum(start - 1)  # so that the result is the sum of arr[start:(end + 1)]
         return ans
 
     def __setitem__(self, idx: int, val: Union[int, float]) -> None:
@@ -132,7 +132,7 @@ def __str__(self) -> str:
         """
         return self.__repr__()
 
-    def __len__(self):
+    def __len__(self) -> int:
         """
         Returns the length of binary indexed tree.
         """

tests/README.md

@@ -0,0 +1 @@
+To run tests from the command line use: python -m pytest --cov=ds/ --cov-report=html:tests/code_coverage