Create count_of_Smaller_Numbers_After_Self.py

Arrays/Count of Smaller Numbers After Self/solution.py

@@ -0,0 +1,31 @@
+from bisect import bisect_left
+from typing import List
+
+
+class Solution:
+    @staticmethod
+    def countSmaller(nums: List[int]) -> List[int]:
+        # get the length of the input array
+        n = len(nums)
+
+        # create an array of zeros with the same length as the input array
+        counts = [0] * n
+
+        # create an empty list to hold the sorted numbers
+        sorted_nums = []
+
+        # loop through the input array in reverse order
+        for i in range(n - 1, -1, -1):
+            # use the bisect_left function to find the index where the current number
+            # should be inserted in the sorted list
+            idx = bisect_left(sorted_nums, nums[i])
+
+            # the number of elements to the right of the current index is equal to the
+            # number of elements that are smaller than the current number
+            counts[i] = idx
+
+            # insert the current number into the sorted list at the correct index
+            sorted_nums.insert(idx, nums[i])
+
+        # return the array of counts
+        return counts

Arrays/Count of Smaller Numbers After Self/test_solution.py

@@ -0,0 +1,36 @@
+import unittest  # importing the unittest module for unit testing
+from solution import Solution
+
+
+class TestSolution(unittest.TestCase):
+
+    def setUp(self):
+        self.solution = Solution()  # creating an instance of the Solution class for testing
+
+    def test_empty_input(self):
+        # testing with empty input
+        nums = []
+        expected_counts = []
+        self.assertEqual(self.solution.countSmaller(nums), expected_counts)
+
+    def test_single_input(self):
+        # testing with a single input
+        nums = [5]
+        expected_counts = [0]
+        self.assertEqual(self.solution.countSmaller(nums), expected_counts)
+
+    def test_multiple_input(self):
+        # testing with multiple inputs
+        nums = [5, 2, 6, 1]
+        expected_counts = [1, 0, 1, 0]
+        self.assertEqual(self.solution.countSmaller(nums), expected_counts)
+
+    def test_duplicate_input(self):
+        # testing with duplicate inputs
+        nums = [1, 2, 2, 3]
+        expected_counts = [0, 0, 0, 2]
+        self.assertEqual(self.solution.countSmaller(nums), expected_counts)
+
+
+if __name__ == '__main__':
+    unittest.main()  # running the test suite using unittest module