80. Remove Duplicates from Sorted Array II

    - Language: Python.
    - Time complexity: O(n+n).
    - Space complexity: O(1).

Author: welder87

python_solutions/lc_80_remove_duplicates_from_sorted_array_2/__init__.py

@@ -0,0 +1,30 @@
+class Solution:
+    def removeDuplicates(self, nums: list[int]) -> int:
+        # Time complexity: O(n + n). Space complexity: O(1).
+        i, j = 0, 1
+        cnt = 1
+        counter = 0
+        # first pass through the array
+        # marking as empty value
+        while i < len(nums) or j < len(nums):
+            while j < len(nums) and nums[i] == nums[j]:
+                cnt += 1
+                if cnt > 2:
+                    nums[j] = None
+                    counter += 1
+                j += 1
+            i = j
+            j += 1
+            cnt = 1
+        j = 1
+        # second pass through the array
+        # moving empty values
+        for i in range(len(nums)):
+            if nums[i] is not None:
+                j += 1
+                continue
+            while j < len(nums) and nums[j] is None:
+                j += 1
+            if j < len(nums):
+                nums[i], nums[j] = nums[j], nums[i]
+        return len(nums) - counter

python_solutions/lc_80_remove_duplicates_from_sorted_array_2/lc_80.py

@@ -0,0 +1,40 @@
+import pytest
+
+from lc_80_remove_duplicates_from_sorted_array_2.lc_80 import Solution
+
+test_cases = (
+    # preset cases
+    ([1, 1, 1, 2, 2, 3], 5, [1, 1, 2, 2, 3, None]),
+    ([0, 0, 1, 1, 1, 1, 2, 3, 3], 7, [0, 0, 1, 1, 2, 3, 3, None, None]),
+    # common cases
+    ([-1, -1, -1, -1, 0, 0, 0, 3, 3, 4], 7, [-1, -1, 0, 0, 3, 3, 4, None, None, None]),
+    (
+        [-1, -1, -1, -1, 0, 0, 0, 3, 3, 4, 4, 4, 4],
+        8,
+        [-1, -1, 0, 0, 3, 3, 4, 4, None, None, None, None, None],
+    ),
+    ([-1, 2, 2, 2, 2, 5], 4, [-1, 2, 2, 5, None, None]),
+    ([-1, -1, -1, -1, -1], 2, [-1, -1, None, None, None]),
+    ([-1, -1, 0, 0, 3, 3], 6, [-1, -1, 0, 0, 3, 3]),
+    # corner cases
+    ([-15], 1, [-15]),
+    ([-15, -15], 2, [-15, -15]),
+    ([0, 0, 0], 2, [0, 0, None]),
+    ([-15, 0, 1, 4], 4, [-15, 0, 1, 4]),
+)
+
+
+@pytest.mark.parametrize(("nums", "ans", "deduplicated_nums"), test_cases)
+def test_success_v0(
+    nums: list[int],
+    ans: int,
+    deduplicated_nums: list[int],
+    solution: Solution,
+):
+    assert solution.removeDuplicates(nums) == ans
+    assert nums == deduplicated_nums
+
+
+@pytest.fixture
+def solution() -> Solution:
+    return Solution()