feat(algorithms, intervals): remove covered intervals #124
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BrianLusina
added
enhancement
Algorithm
WalkthroughAdds a new "Remove Covered Intervals" algorithm module to the codebase, including implementation, documentation, and test suite. The solution uses a greedy approach: sort intervals by start ascending and end descending, then iterate to count intervals not covered by others. Changes
Estimated code review effort🎯 3 (Moderate) | ⏱️ ~20 minutes
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Pre-merge checks and finishing touches❌ Failed checks (1 warning)
✅ Passed checks (2 passed)
✨ Finishing touches
🧪 Generate unit tests (beta)
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Actionable comments posted: 2
🧹 Nitpick comments (3)
algorithms/intervals/remove_intervals/test_remove_covered_intervals.py (1)
91-94: Minor: Method name inconsistency.The test method is named
test_remove_closed_intervalsbut the feature is about "covered" intervals, not "closed" intervals. Consider renaming for consistency with the function under test.🔎 Suggested fix
- def test_remove_closed_intervals(self, intervals: List[List[int]], expected: int): + def test_remove_covered_intervals(self, intervals: List[List[int]], expected: int):algorithms/intervals/remove_intervals/__init__.py (2)
25-30: Misleading comment about space complexity.The comment states "we do not incur any additional space complexity" but Python's
list.sort()(Timsort) uses O(n) auxiliary space in the worst case. While it modifies the list in-place (no new list object), it still requires temporary memory for the merge operations.🔎 Suggested fix
# Sort intervals by start time in ascending order and then by end time in descending order. We sort by the end time # to remove a tie-breaker where two intervals have the same start time. - # This will incur a time complexity of O(nlogn). We sort in place, so, we do not - # incur any additional space complexity by copying over to a new list. The assumption made here is that it is okay - # to mutate the input list. + # This will incur a time complexity of O(n log n) and O(n) auxiliary space for Python's Timsort. + # The assumption made here is that it is okay to mutate the input list. intervals.sort(key=lambda x: (x[0], -x[1]))
42-43: Terminology mismatch in comment.The comment says "non-overlapping intervals" but the function returns the count of "non-covered intervals" per the docstring. These are distinct concepts—intervals can overlap without being covered.
🔎 Suggested fix
- # return the count of non-overlapping intervals + # return the count of non-covered intervals return count
📜 Review details
Configuration used: defaults
Review profile: CHILL
Plan: Pro
⛔ Files ignored due to path filters (12)
algorithms/intervals/remove_intervals/images/examples/remove_covered_intervals_example_1.pngis excluded by!**/*.pngalgorithms/intervals/remove_intervals/images/examples/remove_covered_intervals_example_2.pngis excluded by!**/*.pngalgorithms/intervals/remove_intervals/images/examples/remove_covered_intervals_example_3.pngis excluded by!**/*.pngalgorithms/intervals/remove_intervals/images/examples/remove_covered_intervals_example_4.pngis excluded by!**/*.pngalgorithms/intervals/remove_intervals/images/examples/remove_covered_intervals_example_5.pngis excluded by!**/*.pngalgorithms/intervals/remove_intervals/images/solutions/remove_covered_intervals_solution_1.pngis excluded by!**/*.pngalgorithms/intervals/remove_intervals/images/solutions/remove_covered_intervals_solution_2.pngis excluded by!**/*.pngalgorithms/intervals/remove_intervals/images/solutions/remove_covered_intervals_solution_3.pngis excluded by!**/*.pngalgorithms/intervals/remove_intervals/images/solutions/remove_covered_intervals_solution_4.pngis excluded by!**/*.pngalgorithms/intervals/remove_intervals/images/solutions/remove_covered_intervals_solution_5.pngis excluded by!**/*.pngalgorithms/intervals/remove_intervals/images/solutions/remove_covered_intervals_solution_6.pngis excluded by!**/*.pngalgorithms/intervals/remove_intervals/images/solutions/remove_covered_intervals_solution_7.pngis excluded by!**/*.png
📒 Files selected for processing (4)
DIRECTORY.md(1 hunks)algorithms/intervals/remove_intervals/README.md(1 hunks)algorithms/intervals/remove_intervals/__init__.py(1 hunks)algorithms/intervals/remove_intervals/test_remove_covered_intervals.py(1 hunks)
🧰 Additional context used
🧬 Code graph analysis (1)
algorithms/intervals/remove_intervals/test_remove_covered_intervals.py (1)
algorithms/intervals/remove_intervals/__init__.py (1)
remove_covered_intervals(4-43)
🪛 LanguageTool
algorithms/intervals/remove_intervals/README.md
[grammar] ~64-~64: Ensure spelling is correct
Context: ... time complexity of the solution is O(n logn), where n is the number of intervals. T...
(QB_NEW_EN_ORTHOGRAPHY_ERROR_IDS_1)
[grammar] ~65-~65: Ensure spelling is correct
Context: ...ecause sorting the intervals takes O(n logn) time, and the subsequent iteration thr...
(QB_NEW_EN_ORTHOGRAPHY_ERROR_IDS_1)
[grammar] ~66-~66: Ensure spelling is correct
Context: ...d by the sorting step, resulting in O(n logn). ### Space Complexity The sorting op...
(QB_NEW_EN_ORTHOGRAPHY_ERROR_IDS_1)
[uncategorized] ~70-~70: If this is a compound adjective that modifies the following noun, use a hyphen.
Context: ...n has a space complexity of O(n) in the worst case due to additional memory required for t...
(EN_COMPOUND_ADJECTIVE_INTERNAL)
🪛 markdownlint-cli2 (0.18.1)
DIRECTORY.md
112-112: Unordered list indentation
Expected: 2; Actual: 4
(MD007, ul-indent)
113-113: Unordered list indentation
Expected: 4; Actual: 6
(MD007, ul-indent)
🔇 Additional comments (4)
DIRECTORY.md (1)
112-113: LGTM!The new "Remove Intervals" entry is correctly added under the Intervals section with proper indentation matching the existing file structure. The link to the test file follows the established convention.
algorithms/intervals/remove_intervals/test_remove_covered_intervals.py (1)
1-5: Good defensive testing practice.The use of
deepcopyon line 92 correctly protects against the in-place mutation documented in the implementation. This ensures test inputs remain unchanged between test runs and prevents false positives.algorithms/intervals/remove_intervals/README.md (1)
68-72: Space complexity explanation is accurate.The README correctly notes O(n) space for Python's Timsort. However, the implementation comment on line 27-28 claims "We sort in place, so, we do not incur any additional space complexity" which is misleading. Python's
list.sort()uses O(n) auxiliary space internally despite being "in-place" (modifying the original list). The documentation here is more accurate than the code comment.algorithms/intervals/remove_intervals/__init__.py (1)
4-43: Well-implemented greedy algorithm.The implementation correctly handles:
- Empty input with early return
- Tie-breaking when intervals share the same start by sorting end in descending order
- Tracking maximum end seen to identify non-covered intervals
The algorithm is O(n log n) time complexity and the logic is sound.
| - 1 <= intervals.length <= 10^4 | ||
| - intervals[i].length == 2 | ||
| - 0 <= li < ri <= 10^5 | ||
| - All the give intervals are unique |
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Minor typo in constraints.
"give" should be "given".
🔎 Suggested fix
-- All the give intervals are unique
+- All the given intervals are unique📝 Committable suggestion
‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.
| - All the give intervals are unique | |
| - All the given intervals are unique |
🤖 Prompt for AI Agents
In algorithms/intervals/remove_intervals/README.md around line 14, there's a
typo in the constraints: replace "All the give intervals are unique" with "All
the given intervals are unique" to correct the grammar; update the sentence
accordingly and save the README.
| 1. If the start points are the same, sort the intervals by the start point in ascending order, otherwise, sort by the | ||
| endpoint in descending order to prioritize longer intervals. | ||
| 2. Initialize the count with zero to track the remaining (non-covered) intervals. | ||
| 3. Initialize prev_end with zero to track the maximum end value we’ve seen.. |
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Documentation inconsistency with implementation.
The README states "Initialize prev_end with zero" but the implementation initializes max_end_seen with float('-inf'). While both work correctly for this problem (since intervals have non-negative bounds per constraints), the documentation should match the actual implementation for clarity.
🔎 Suggested fix
-3. Initialize prev_end with zero to track the maximum end value we've seen..
+3. Initialize prev_end with negative infinity to track the maximum end value we've seen. 🤖 Prompt for AI Agents
In algorithms/intervals/remove_intervals/README.md around line 42, the README
says "Initialize prev_end with zero" but the implementation initializes
max_end_seen with float('-inf'); update the README to match the implementation
by changing the documentation text to say "Initialize max_end_seen with
float('-inf')" (or otherwise mention that the code uses negative infinity) so
docs and code agree, or alternatively change the implementation to initialize
with 0 if you prefer that convention — ensure both places use the same variable
name and value.
Describe your change:
Adds an algorithm for removing the covered intervals.
Checklist:
Fixes: #{$ISSUE_NO}.Summary by CodeRabbit
New Features
Documentation
Tests
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