feat(arrays, binary-search): two sum less k #109
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BrianLusina added enhancement Algorithm 
| Caution Review failedThe pull request is closed. WalkthroughAdds a new "Two Sum Less Than K" implementation, README, and tests; updates DIRECTORY.md to include the new entry; and changes Changes
Sequence Diagram(s)sequenceDiagram participant Caller participant two_sum_less_than_k as "two_sum_less_than_k\n(module)" participant sort as "sort()" participant search as "search() (binary search)" Caller->>two_sum_less_than_k: two_sum_less_than_k(nums, k) two_sum_less_than_k->>sort: sort nums ascending sort-->>two_sum_less_than_k: sorted nums loop iterate x over indices two_sum_less_than_k->>search: search(sorted, k - nums[x], start=x+1) search-->>two_sum_less_than_k: index y or -1 alt y != -1 two_sum_less_than_k->>two_sum_less_than_k: update max_sum = max(max_sum, nums[x]+nums[y]) end end two_sum_less_than_k-->>Caller: return max_sum or -1 Estimated code review effort🎯 3 (Moderate) | ⏱️ ~20 minutes
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Actionable comments posted: 2
🧹 Nitpick comments (2)
DIRECTORY.md (1)
26-27: Clarify the test link label to avoid confusion.Line 27 uses the same label "Test Two Sum" as line 25, making it difficult to distinguish between the regular Two Sum tests and the Two Sum Less K tests.
Consider updating the label to be more specific:
* Two Sum Less K - * [Test Two Sum](https://github.com/BrianLusina/PythonSnips/blob/master/algorithms/arrays/two_sum_less_k/test_two_sum.py) + * [Test Two Sum Less K](https://github.com/BrianLusina/PythonSnips/blob/master/algorithms/arrays/two_sum_less_k/test_two_sum.py)algorithms/arrays/two_sum_less_k/__init__.py (1)
30-56: Consider whethersearchshould be a private helper.The
searchfunction is currently exported from the module but appears to be an internal implementation detail used only bytwo_sum_less_than_k.If this function is not intended for external use, consider prefixing it with an underscore to indicate it's private:
-def search(nums: List[int], target: int, start: int) -> int: +def _search(nums: List[int], target: int, start: int) -> int:Then update the call on line 22:
- y = search(nums, k - nums[x], x + 1) + y = _search(nums, k - nums[x], x + 1)However, if you intend for
searchto be part of the public API for reuse in other contexts, the current implementation is fine.
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DIRECTORY.md(1 hunks)algorithms/arrays/two_sum/__init__.py(1 hunks)algorithms/arrays/two_sum_less_k/README.md(1 hunks)algorithms/arrays/two_sum_less_k/__init__.py(1 hunks)algorithms/arrays/two_sum_less_k/test_two_sum.py(1 hunks)
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algorithms/arrays/two_sum_less_k/test_two_sum.py (1)
algorithms/arrays/two_sum_less_k/__init__.py (1)
two_sum_less_than_k(4-27)
🪛 markdownlint-cli2 (0.18.1)
DIRECTORY.md
26-26: Unordered list indentation
Expected: 2; Actual: 4
(MD007, ul-indent)
27-27: Unordered list indentation
Expected: 4; Actual: 6
(MD007, ul-indent)
🔇 Additional comments (2)
algorithms/arrays/two_sum/__init__.py (1)
30-30: LGTM! Good improvement for clarity.Explicitly returning an empty list is more clear and consistent than relying on implicit
Nonereturn. This makes the function's contract explicit.algorithms/arrays/two_sum_less_k/test_two_sum.py (1)
1-48: LGTM! Comprehensive test coverage.The test suite provides excellent coverage with five well-chosen test cases:
- Standard scenarios with valid pairs
- Edge cases where no valid pair exists (correctly expecting -1)
- Arrays with duplicate values
- Various input sizes
The tests are clear, well-documented, and follow unittest conventions.
| def two_sum_less_than_k(nums: List[int], k: int) -> int: | ||
| """ | ||
| Finds the maximum sum of two elements in a given list of numbers that is less than k. | ||
| Uses binary search to achieve a time complexity of O(n log n) and find the maximum sum of two elements | ||
| that is less than k. It takes the nums array and the target value k as input. | ||
| Args: | ||
| nums (List[int]): A sorted list of integers | ||
| k int: The target value to search for | ||
| Returns: | ||
| The maximum sum of two elements that is less than k | ||
| """ | ||
| max_sum = -1 | ||
| | ||
| # sort the numbers in ascending order to facilitate binary search | ||
| nums.sort() | ||
| | ||
| for x in range(len(nums)): | ||
| # find the maximum sum of two elements that is less than k, with the first element being nums[x] | ||
| y = search(nums, k - nums[x], x + 1) | ||
| if y > x: | ||
| # update max_sum with the maximum sum found so far | ||
| max_sum = max(max_sum, nums[x] + nums[y]) | ||
| | ||
| return max_sum |
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🛠️ Refactor suggestion | 🟠 Major
Fix misleading docstring about input requirements.
Line 10 states that nums should be "A sorted list of integers", but the function sorts the input on line 18. The input does not need to be pre-sorted.
Update the docstring to reflect the actual requirement:
Args: - nums (List[int]): A sorted list of integers + nums (List[int]): A list of integers (will be sorted internally) k int: The target value to search for🤖 Prompt for AI Agents
In algorithms/arrays/two_sum_less_k/__init__.py around lines 4 to 27, the docstring incorrectly says nums is "A sorted list of integers" while the function sorts nums internally; update the docstring to state that nums is an unsorted list of integers (or simply a list of integers) and that the function will sort it as part of its operation, and correct the Args section formatting for k (e.g., "k (int): target value") and the Returns description to clearly state it returns the maximum sum of two elements less than k or -1 if none exist. 
Describe your change:
Adds an algorithm to fund two elements from an unsorted array whose sum is less than the target integer k
Checklist:
Fixes: #{$ISSUE_NO}.Summary by CodeRabbit
New Features
Bug Fixes
Documentation
Tests
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