Add solutions and explanations for problems 3643, 3644, 3645, 3648, 3649, 3653, 3675, 3690, 3694, 3698 #125
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…649, 3653, 3675, 3690, 3694, 3698
Reviewer's GuideAdds Python implementations and English explanations for ten recent LeetCode problems (3643, 3644, 3645, 3648, 3649, 3653, 3675, 3690, 3694, 3698), each following the repository’s standard solution/explanation structure. Class diagram for newly added LeetCode solution classesclassDiagram
class Solution3643 {
+reverseSubmatrix(grid, x, y, k)
}
class Solution3644 {
+sortPermutation(nums)
}
class Solution3645 {
+maxTotal(value, limit)
}
class Solution3648 {
+minSensors(n, m, k)
}
class Solution3649 {
+perfectPairs(nums)
}
class Solution3653 {
+xorAfterQueries(nums, queries)
}
class Solution3675 {
+minOperations(s)
}
class Solution3690 {
+minSplitMerge(nums1, nums2)
}
class Solution3694 {
+distinctPoints(s, k)
}
class Solution3698 {
+splitArray(nums)
}
%% All solution classes are independent utility classes for individual problems
Solution3643 ..> Solution3644 : independent
Solution3644 ..> Solution3645 : independent
Solution3645 ..> Solution3648 : independent
Solution3648 ..> Solution3649 : independent
Solution3649 ..> Solution3653 : independent
Solution3653 ..> Solution3675 : independent
Solution3675 ..> Solution3690 : independent
Solution3690 ..> Solution3694 : independent
Solution3694 ..> Solution3698 : independent
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Note Other AI code review bot(s) detectedCodeRabbit has detected other AI code review bot(s) in this pull request and will avoid duplicating their findings in the review comments. This may lead to a less comprehensive review. WalkthroughAdds 10 new explanation Markdown files and 10 new Python solution implementations, each pairing an explanation with a corresponding algorithmic solution covering distinct problems (grid flips, bitwise permutation mask, heap grouping, sensor coverage, pair counting, query transforms, circular string shifts, split-and-merge BFS, sliding-window endpoints, and mountain-array splitting). Changes
Estimated code review effort🎯 3 (Moderate) | ⏱️ ~25 minutes
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🧰 Additional context used🪛 Ruff (0.14.8)solutions/3643/01.py3-3: Undefined name (F821) 3-3: Undefined name (F821) 4-4: Undefined name (F821) 4-4: Undefined name (F821) 5-5: Comment contains ambiguous (RUF003) ⏰ Context from checks skipped due to timeout of 90000ms. You can increase the timeout in your CodeRabbit configuration to a maximum of 15 minutes (900000ms). (1)
🔇 Additional comments (1)
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Hey there - I've reviewed your changes and found some issues that need to be addressed.
- In
solutions/3690/01.py, the split-and-merge BFS successor generation looks incorrect:new_state = prefix[:pos] + removed + prefix[pos:] + suffixindexesposonly intoprefixinstead of into the concatenatedprefix+suffix, so many insertion positions are never explored; consider buildingbase = prefix + suffixand insertingremovedintobaseat every index. - In
solutions/3694/01.py, the sliding-window simulation does not account for the moves before the removed substring or after it for each possible removal position; starting from(0,0)and only updating by adding/removing the window endpoints effectively models removing a prefix, not an arbitrary length-k substring, so the transition logic needs to be reworked to incorporate both prefix and suffix contributions for each candidate window. - In
solutions/3649/01.py, the function never returnsresat the end ofperfectPairs, so it currently always returnsNone; add areturn resafter the loop to actually output the computed pair count.
Prompt for AI Agents
Please address the comments from this code review:
## Overall Comments
- In `solutions/3690/01.py`, the split-and-merge BFS successor generation looks incorrect: `new_state = prefix[:pos] + removed + prefix[pos:] + suffix` indexes `pos` only into `prefix` instead of into the concatenated `prefix+suffix`, so many insertion positions are never explored; consider building `base = prefix + suffix` and inserting `removed` into `base` at every index.
- In `solutions/3694/01.py`, the sliding-window simulation does not account for the moves before the removed substring or after it for each possible removal position; starting from `(0,0)` and only updating by adding/removing the window endpoints effectively models removing a prefix, not an arbitrary length-k substring, so the transition logic needs to be reworked to incorporate both prefix and suffix contributions for each candidate window.
- In `solutions/3649/01.py`, the function never returns `res` at the end of `perfectPairs`, so it currently always returns `None`; add a `return res` after the loop to actually output the computed pair count.
## Individual Comments
### Comment 1
<location> `solutions/3690/01.py:27` </location>
<code_context>
+
+ # Try inserting at all possible positions
+ for pos in range(len(prefix) + len(suffix) + 1):
+ new_state = prefix[:pos] + removed + prefix[pos:] + suffix
+ new_state_tuple = tuple(new_state)
+
</code_context>
<issue_to_address>
**issue (bug_risk):** The insertion logic never places `removed` inside the `suffix` segment, which likely misses reachable states.
Because `prefix[:pos] + removed + prefix[pos:] + suffix` only slices `prefix`, any `pos > len(prefix)` still uses the full `prefix` on both sides, so `removed` is never inserted within `suffix`. To truly iterate over all positions, use the full state when slicing (e.g. `state[:pos] + removed + state[pos:]`) or explicitly handle prefix vs. suffix indices separately.
</issue_to_address>
### Comment 2
<location> `solutions/3649/01.py:19` </location>
<code_context>
+ j += 1
+ # Count pairs: all indices between i+1 and j-1 form valid pairs with i
+ # j points to first element > 2*arr[i], so valid pairs are from i+1 to j-1
+ res += max(0, j - i - 1)
+
</code_context>
<issue_to_address>
**issue (bug_risk):** The function never returns `res`, so it implicitly returns `None`.
Add a `return res` at the end of `perfectPairs` so callers receive the computed value instead of `None`.
</issue_to_address>
### Comment 3
<location> `explanations/3644/en.md:46-49` </location>
<code_context>
+|-------|-------|----------|-------------|------------|
+| 0 | 0 | Yes (0==0) | Skip | (1<<30)-1 |
+| 1 | 3 | No (3≠1) | mask &= 3 | 3 |
+| 2 | 2 | No (2≠2) | mask &= 2 | 3 & 2 = 2 |
+| 3 | 1 | No (1≠3) | mask &= 1 | 2 & 1 = 0 |
+
</code_context>
<issue_to_address>
**issue (typo):** Element at index 2 is incorrectly marked as misplaced and the `2≠2` comparison is a typo.
In this row, `2` at index 2 is correctly placed (`2 == 2`), so it should be marked as correct rather than `No (2≠2)`, and the `2≠2` text should be removed or fixed.
```suggestion
| Index | Value | Correct? | Mask Update | Mask Value |
|-------|-------|----------|-------------|------------|
| 0 | 0 | Yes (0==0) | Skip | (1<<30)-1 |
| 1 | 3 | No (3≠1) | mask &= 3 | 3 |
| 2 | 2 | Yes (2==2) | Skip | 3 |
| 3 | 1 | No (1≠3) | mask &= 1 | 3 & 1 = 1 |
```
</issue_to_address>
### Comment 4
<location> `explanations/3644/en.md:53` </location>
<code_context>
+| 2 | 2 | No (2≠2) | mask &= 2 | 3 & 2 = 2 |
+| 3 | 1 | No (1≠3) | mask &= 1 | 2 & 1 = 0 |
+
+The final mask is 0, which means k=0 (allowing any swap) works. However, we want the maximum k. The key insight is that we can use correctly placed elements as bridges. For [0,3,2,1], we can swap 3 and 1 directly (3 & 1 = 1), so k=1 works. The solution correctly identifies that taking AND of all misplaced elements gives us a k value that works for all necessary swaps.
+
</code_context>
<issue_to_address>
**issue:** Explanation of the final mask and the maximum k is internally inconsistent.
You derive a final mask of 0 (implying k=0), but then claim k=1 works for the example and that AND-ing all misplaced elements “correctly” yields a working k. In the walkthrough, the AND procedure never actually produces 1. Please align the example and mask computation with the described strategy, or explicitly describe the algorithm that yields k=1 and how the chosen elements to AND correspond to that result.
</issue_to_address>Help me be more useful! Please click 👍 or 👎 on each comment and I'll use the feedback to improve your reviews.
|
|
||
| # Try inserting at all possible positions | ||
| for pos in range(len(prefix) + len(suffix) + 1): | ||
| new_state = prefix[:pos] + removed + prefix[pos:] + suffix |
There was a problem hiding this comment.
issue (bug_risk): The insertion logic never places removed inside the suffix segment, which likely misses reachable states.
Because prefix[:pos] + removed + prefix[pos:] + suffix only slices prefix, any pos > len(prefix) still uses the full prefix on both sides, so removed is never inserted within suffix. To truly iterate over all positions, use the full state when slicing (e.g. state[:pos] + removed + state[pos:]) or explicitly handle prefix vs. suffix indices separately.
| j += 1 | ||
| # Count pairs: all indices between i+1 and j-1 form valid pairs with i | ||
| # j points to first element > 2*arr[i], so valid pairs are from i+1 to j-1 | ||
| res += max(0, j - i - 1) |
There was a problem hiding this comment.
issue (bug_risk): The function never returns res, so it implicitly returns None.
Add a return res at the end of perfectPairs so callers receive the computed value instead of None.
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Actionable comments posted: 11
🧹 Nitpick comments (4)
solutions/3645/01.py (1)
12-12: Remove unused variableactive_count.The variable
active_countis assigned but never used in the logic. Consider removing it to improve code clarity.🔎 Proposed fix
res = 0 - active_count = 0 # Process groups in order of limit (smallest first) for limit_val in sorted(groups.keys()):# Sum all values in heap and add to result res += sum(heap) - active_count += len(heap) return resAlso applies to: 25-25
explanations/3645/en.md (1)
38-54: Consider adding a more illustrative example.The current example has only one value per limit group, which doesn't demonstrate the min-heap behavior when the heap size exceeds the limit. Consider adding an example where multiple values share the same limit to better illustrate the heap's eviction mechanism.
solutions/3690/01.py (1)
18-18: Consider renaming ambiguous variablel.The variable name
l(lowercase L) can be easily confused with1(digit one) orI(uppercase i) in many fonts.🔎 Suggested refactor
# Try all possible split-and-merge operations n = len(state) - for l in range(n): - for r in range(l, n): + for left in range(n): + for right in range(left, n): # Remove subarray [l..r] - removed = state[l:r+1] - prefix = state[:l] - suffix = state[r+1:] + removed = state[left:right+1] + prefix = state[:left] + suffix = state[right+1:]explanations/3694/en.md (1)
45-60: Clarify the trace walkthrough for accuracy.The trace walkthrough for
s = "LUL",k = 1appears inconsistent:
Line 48 mentions position
(0,1), but tracing through the removals:
- Remove
s[0]="L"→ execute "UL" → final position(-1,1)- Remove
s[1]="U"→ execute "LL" → final position(-2,0)- Remove
s[2]="L"→ execute "LU" → final position(-1,1)- Distinct:
{(-1,1), (-2,0)}= 2 positionsLine 59 mentions "initial (0,0)" but this only occurs when
k = n(all moves removed), which isn't the case in this example.Consider revising the trace to show each removal explicitly with the resulting move sequence and final coordinate to improve clarity.
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📒 Files selected for processing (20)
explanations/3643/en.md(1 hunks)explanations/3644/en.md(1 hunks)explanations/3645/en.md(1 hunks)explanations/3648/en.md(1 hunks)explanations/3649/en.md(1 hunks)explanations/3653/en.md(1 hunks)explanations/3675/en.md(1 hunks)explanations/3690/en.md(1 hunks)explanations/3694/en.md(1 hunks)explanations/3698/en.md(1 hunks)solutions/3643/01.py(1 hunks)solutions/3644/01.py(1 hunks)solutions/3645/01.py(1 hunks)solutions/3648/01.py(1 hunks)solutions/3649/01.py(1 hunks)solutions/3653/01.py(1 hunks)solutions/3675/01.py(1 hunks)solutions/3690/01.py(1 hunks)solutions/3694/01.py(1 hunks)solutions/3698/01.py(1 hunks)
🧰 Additional context used
🧬 Code graph analysis (1)
solutions/3653/01.py (1)
visualizations/3623/01.jsx (1)
MOD(39-39)
🪛 LanguageTool
explanations/3648/en.md
[style] ~28-~28: Three successive sentences begin with the same word. Consider rewording the sentence or use a thesaurus to find a synonym.
Context: ...needed horizontally: ceil(n / size). 3. Calculate sensors needed vertically: ceil(m / siz...
(ENGLISH_WORD_REPEAT_BEGINNING_RULE)
explanations/3690/en.md
[style] ~9-~9: As an alternative to the over-used intensifier ‘very’, consider replacing this phrase.
Context: ...nput Size:** Array length is at most 6 (very small). - Time Complexity: O(6! * 6^2) in...
(EN_WEAK_ADJECTIVE)
🪛 Ruff (0.14.8)
solutions/3649/01.py
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solutions/3643/01.py
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3-3: Comment contains ambiguous × (MULTIPLICATION SIGN). Did you mean x (LATIN SMALL LETTER X)?
(RUF003)
solutions/3653/01.py
2-2: Undefined name List
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2-2: Undefined name List
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2-2: Undefined name List
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6-6: Ambiguous variable name: l
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solutions/3644/01.py
2-2: Undefined name List
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solutions/3645/01.py
2-2: Undefined name List
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2-2: Undefined name List
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8-8: Loop control variable i not used within loop body
Rename unused i to _i
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8-8: Ambiguous variable name: l
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8-8: zip() without an explicit strict= parameter
Add explicit value for parameter strict=
(B905)
solutions/3698/01.py
2-2: Undefined name List
(F821)
4-4: Ambiguous variable name: l
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12-12: Ambiguous variable name: l
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solutions/3690/01.py
2-2: Undefined name List
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2-2: Undefined name List
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18-18: Ambiguous variable name: l
(E741)
⏰ Context from checks skipped due to timeout of 90000ms. You can increase the timeout in your CodeRabbit configuration to a maximum of 15 minutes (900000ms). (1)
- GitHub Check: Sourcery review
🔇 Additional comments (10)
solutions/3675/01.py (1)
1-8: LGTM!The implementation correctly computes the circular distance from 'a' for each character and returns the maximum. The logic is clean and efficient.
solutions/3648/01.py (1)
1-6: LGTM!The implementation correctly calculates the minimum number of sensors using ceiling division. The formula is efficient and mathematically sound.
explanations/3643/en.md (1)
1-56: LGTM! Clear and well-structured explanation.The explanation provides a comprehensive walkthrough of the vertical submatrix flip strategy with appropriate complexity analysis, example trace, and final result verification.
explanations/3698/en.md (1)
1-64: LGTM! Well-documented two-pointer approach.The explanation clearly outlines the strategy for finding the optimal split point in a mountain array with detailed trace walkthrough and complexity analysis.
explanations/3649/en.md (1)
1-52: LGTM! Clear two-pointer strategy for pair counting.The explanation effectively describes the optimization from O(n²) brute force to O(n log n) with sorting and two pointers, including a detailed trace walkthrough.
explanations/3653/en.md (1)
1-64: LGTM! Straightforward simulation approach.The explanation clearly documents the query processing strategy with appropriate complexity analysis and a complete example walkthrough.
explanations/3690/en.md (1)
1-64: LGTM! Comprehensive BFS strategy explanation.The explanation clearly documents the state-space exploration approach with appropriate complexity analysis for the small input constraint. The example walkthrough effectively demonstrates the operation.
explanations/3648/en.md (1)
1-58: LGTM! Clear mathematical approach for sensor coverage.The explanation effectively describes the optimal grid tiling strategy with straightforward arithmetic calculation, including appropriate complexity analysis and example verification.
explanations/3675/en.md (1)
1-57: LGTM!The explanation clearly describes the circular alphabet distance strategy. The mathematical formulas and trace walkthrough are accurate, and the complexity analysis is appropriate for the problem.
solutions/3690/01.py (1)
16-32: Constraint assumption is incorrect.The array length is at most 6, making the O(n⁴) approach entirely acceptable. With n ≤ 6, the algorithm generates at most 1,296 operations per BFS level, which poses no performance concern. The BFS solution is appropriate for this problem.
Likely an incorrect or invalid review comment.
| | Index | Value | Correct? | Mask Update | Mask Value | | ||
| |-------|-------|----------|-------------|------------| | ||
| | 0 | 0 | Yes (0==0) | Skip | (1<<30)-1 | | ||
| | 1 | 3 | No (3≠1) | mask &= 3 | 3 | | ||
| | 2 | 2 | No (2≠2) | mask &= 2 | 3 & 2 = 2 | | ||
| | 3 | 1 | No (1≠3) | mask &= 1 | 2 & 1 = 0 | |
There was a problem hiding this comment.
Correctness error in trace table (line 50).
The table incorrectly marks index 2 as misplaced:
| Index | Value | Correct? | Mask Update | Mask Value |
|---|---|---|---|---|
| 2 | 2 | No (2≠2) | mask &= 2 | 3 & 2 = 2 |
Since 2 == 2, the element at index 2 is correctly placed. The row should indicate "Yes (2==2)" and "Skip" for the mask update.
Corrected trace:
For nums = [0,3,2,1]:
- Index 0: value 0, correct (0==0) → Skip
- Index 1: value 3, incorrect (3≠1) → mask &= 3 → mask = 3
- Index 2: value 2, correct (2==2) → Skip
- Index 3: value 1, incorrect (1≠3) → mask &= 1 → mask = 3 & 1 = 1
The final mask should be 1, not 0.
🤖 Prompt for AI Agents
In explanations/3644/en.md around lines 46 to 51, the trace table incorrectly
marks index 2 as misplaced; change the row for index 2 to show "Yes (2==2)" and
"Skip" for the mask update, and update subsequent mask calculations accordingly
so the final mask becomes 1 instead of 0 (adjust the narrative and the mask
value cells for index 3 to reflect mask = 3 & 1 = 1).
solutions/3643/01.py
Outdated
| class Solution: | ||
| def reverseSubmatrix(self, grid: List[List[int]], x: int, y: int, k: int) -> List[List[int]]: |
There was a problem hiding this comment.
Add missing import for type hints.
The List type hint is used but not imported, causing a NameError at runtime when type hints are evaluated.
🔎 Proposed fix
+from typing import List
+
class Solution:
def reverseSubmatrix(self, grid: List[List[int]], x: int, y: int, k: int) -> List[List[int]]:📝 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.
| class Solution: | |
| def reverseSubmatrix(self, grid: List[List[int]], x: int, y: int, k: int) -> List[List[int]]: | |
| from typing import List | |
| class Solution: | |
| def reverseSubmatrix(self, grid: List[List[int]], x: int, y: int, k: int) -> List[List[int]]: |
🧰 Tools
🪛 Ruff (0.14.8)
2-2: Undefined name List
(F821)
2-2: Undefined name List
(F821)
2-2: Undefined name List
(F821)
2-2: Undefined name List
(F821)
🤖 Prompt for AI Agents
In solutions/3643/01.py around lines 1 to 2, the function signature uses the
List type hint but List is not imported, causing a NameError when evaluating
annotations; add the missing import (e.g., from typing import List) at the top
of the file so that List is defined for type hints.
| class Solution: | ||
| def sortPermutation(self, nums: List[int]) -> int: |
There was a problem hiding this comment.
Add missing import for type hints.
The List type hint is used but not imported, which will cause a NameError at runtime when type hints are evaluated.
🔎 Proposed fix
+from typing import List
+
class Solution:
def sortPermutation(self, nums: List[int]) -> int:📝 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.
| class Solution: | |
| def sortPermutation(self, nums: List[int]) -> int: | |
| from typing import List | |
| class Solution: | |
| def sortPermutation(self, nums: List[int]) -> int: |
🧰 Tools
🪛 Ruff (0.14.8)
2-2: Undefined name List
(F821)
🤖 Prompt for AI Agents
In solutions/3644/01.py around lines 1 to 2, the function uses the type hint
List but the List symbol is not imported; add the missing import by importing
List (e.g., from typing import List) at the top of the file so the type hint
resolves correctly and avoids a NameError.
| class Solution: | ||
| def maxTotal(self, value: List[int], limit: List[int]) -> int: |
There was a problem hiding this comment.
Add missing import for type hints.
The List type hint is used but not imported, causing a NameError at runtime when type hints are evaluated.
🔎 Proposed fix
+from typing import List
+
class Solution:
def maxTotal(self, value: List[int], limit: List[int]) -> int:🧰 Tools
🪛 Ruff (0.14.8)
2-2: Undefined name List
(F821)
2-2: Undefined name List
(F821)
🤖 Prompt for AI Agents
In solutions/3645/01.py around lines 1 to 2, the type hint List is referenced
but not imported, causing a NameError; fix by adding the missing import
statement (e.g., add "from typing import List") at the top of the file before
the Solution class so the type hint resolves correctly.
| class Solution: | ||
| def perfectPairs(self, nums: List[int]) -> int: |
There was a problem hiding this comment.
Add missing import for type hints.
The List type hint is used but not imported, causing a NameError at runtime when type hints are evaluated.
🔎 Proposed fix
+from typing import List
+
class Solution:
def perfectPairs(self, nums: List[int]) -> int:📝 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.
| class Solution: | |
| def perfectPairs(self, nums: List[int]) -> int: | |
| from typing import List | |
| class Solution: | |
| def perfectPairs(self, nums: List[int]) -> int: |
🧰 Tools
🪛 Ruff (0.14.8)
2-2: Undefined name List
(F821)
🤖 Prompt for AI Agents
In solutions/3649/01.py around lines 1 to 2, the function signature uses the
type hint List but List is not imported; add the missing import by adding "from
typing import List" (or using built-in list annotation if targeting Python 3.9+)
at the top of the file so the type hint resolves and avoids NameError.
| class Solution: | ||
| def xorAfterQueries(self, nums: List[int], queries: List[List[int]]) -> int: |
There was a problem hiding this comment.
Add missing import for type hints.
The List type hint is used but not imported, which will cause a NameError at runtime when the type hints are evaluated.
🔎 Proposed fix
+from typing import List
+
class Solution:
def xorAfterQueries(self, nums: List[int], queries: List[List[int]]) -> int:📝 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.
| class Solution: | |
| def xorAfterQueries(self, nums: List[int], queries: List[List[int]]) -> int: | |
| from typing import List | |
| class Solution: | |
| def xorAfterQueries(self, nums: List[int], queries: List[List[int]]) -> int: |
🧰 Tools
🪛 Ruff (0.14.8)
2-2: Undefined name List
(F821)
2-2: Undefined name List
(F821)
2-2: Undefined name List
(F821)
🤖 Prompt for AI Agents
In solutions/3653/01.py around lines 1 to 2, the function signature uses the
List type hint but List is not imported; add the missing import by adding "from
typing import List" at the top of the file (before the class) so the type hint
resolves correctly.
| class Solution: | ||
| def minSplitMerge(self, nums1: List[int], nums2: List[int]) -> int: |
There was a problem hiding this comment.
Missing import for List type hint.
The List type from the typing module is used in the method signature but never imported, which will cause a NameError at runtime.
🔎 Proposed fix
+from typing import List
+
class Solution:
def minSplitMerge(self, nums1: List[int], nums2: List[int]) -> int:🧰 Tools
🪛 Ruff (0.14.8)
2-2: Undefined name List
(F821)
2-2: Undefined name List
(F821)
🤖 Prompt for AI Agents
In solutions/3690/01.py around lines 1 to 2, the function signature uses the
List type hint but the List symbol is not imported; add the missing import by
importing List from the typing module at the top of the file (e.g., add "from
typing import List") so the type annotation resolves and avoids a NameError.
| for l in range(n): | ||
| for r in range(l, n): | ||
| # Remove subarray [l..r] | ||
| removed = state[l:r+1] | ||
| prefix = state[:l] | ||
| suffix = state[r+1:] | ||
|
|
||
| # Try inserting at all possible positions | ||
| for pos in range(len(prefix) + len(suffix) + 1): | ||
| new_state = prefix[:pos] + removed + prefix[pos:] + suffix | ||
| new_state_tuple = tuple(new_state) | ||
|
|
||
| if new_state_tuple not in visited: | ||
| visited.add(new_state_tuple) | ||
| queue.append((new_state_tuple, ops + 1)) |
There was a problem hiding this comment.
Critical logic error in state generation (line 27).
After removing state[l:r+1], the remaining elements are prefix + suffix. When inserting removed at position pos, the insertion should happen within the concatenated remaining array. However, line 27 incorrectly inserts into prefix only:
new_state = prefix[:pos] + removed + prefix[pos:] + suffixWhen pos > len(prefix), this produces prefix + removed + suffix, which only inserts after the prefix, not at the intended position within the remaining array.
Example:
state = (1, 2, 3, 4, 5), remove indices [1:2] →removed = (2, 3),prefix = (1,),suffix = (4, 5)- Remaining array:
(1, 4, 5) - To insert at
pos=2in remaining: should get(1, 4, 2, 3, 5) - Current code with
pos=2:prefix[:2] + removed + prefix[2:] + suffix = (1,) + (2, 3) + () + (4, 5) = (1, 2, 3, 4, 5)✗
🔎 Proposed fix
# Try inserting at all possible positions
+ remaining = prefix + suffix
for pos in range(len(prefix) + len(suffix) + 1):
- new_state = prefix[:pos] + removed + prefix[pos:] + suffix
+ new_state = remaining[:pos] + removed + remaining[pos:]
new_state_tuple = tuple(new_state)🧰 Tools
🪛 Ruff (0.14.8)
18-18: Ambiguous variable name: l
(E741)
🤖 Prompt for AI Agents
In solutions/3690/01.py around lines 18 to 32, the code inserts the removed
slice into only the prefix which breaks insertion positions beyond the prefix;
compute the remaining sequence as remaining = prefix + suffix and then build the
new state by inserting removed into remaining at pos: new_state =
remaining[:pos] + removed + remaining[pos:], and iterate pos from 0 to
len(remaining) inclusive so all insertion positions in the concatenated
remaining array are considered.
| # Sliding window: simulate removing each substring of length k | ||
| # Start by processing characters from k onwards | ||
| for i in range(k, len(s)): | ||
| # Add effect of new character at position i | ||
| if s[i] == 'U': | ||
| y += 1 | ||
| elif s[i] == 'D': | ||
| y -= 1 | ||
| elif s[i] == 'L': | ||
| x -= 1 | ||
| elif s[i] == 'R': | ||
| x += 1 | ||
|
|
||
| # Remove effect of character at position i - k (leaving the window) | ||
| if s[i - k] == 'U': | ||
| y -= 1 | ||
| elif s[i - k] == 'D': | ||
| y += 1 | ||
| elif s[i - k] == 'L': | ||
| x += 1 | ||
| elif s[i - k] == 'R': | ||
| x -= 1 | ||
|
|
||
| seen.add((x, y)) |
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🧩 Analysis chain
🏁 Script executed:
python3 << 'EOF'
def distinctPoints_current(s: str, k: int) -> int:
"""Current implementation from the PR"""
seen = {(0, 0)}
x = y = 0
for i in range(k, len(s)):
if s[i] == 'U':
y += 1
elif s[i] == 'D':
y -= 1
elif s[i] == 'L':
x -= 1
elif s[i] == 'R':
x += 1
if s[i - k] == 'U':
y -= 1
elif s[i - k] == 'D':
y += 1
elif s[i - k] == 'L':
x += 1
elif s[i - k] == 'R':
x -= 1
seen.add((x, y))
return len(seen)
def distinctPoints_bruteforce(s: str, k: int) -> int:
"""Brute force: try removing each k-length substring"""
seen = {(0, 0)}
for start in range(len(s) - k + 1):
# Remove substring s[start:start+k]
remaining = s[:start] + s[start+k:]
x = y = 0
for ch in remaining:
if ch == 'U':
y += 1
elif ch == 'D':
y -= 1
elif ch == 'L':
x -= 1
elif ch == 'R':
x += 1
seen.add((x, y))
return len(seen)
# Test cases
test_cases = [
("UDLR", 2),
("UURR", 2),
("UDLR", 1),
("UUDD", 2),
]
for s, k in test_cases:
current = distinctPoints_current(s, k)
brute = distinctPoints_bruteforce(s, k)
match = "✓" if current == brute else "✗"
print(f"{match} s='{s}', k={k}: current={current}, brute={brute}")
EOFRepository: romankurnovskii/leetcode-apps
Length of output: 216
The sliding window implementation fails to correctly track all k-length substring removals.
Test verification reveals the algorithm produces incorrect results for multiple cases: s='UURR' with k=2 returns 3 distinct points instead of 4, and s='UDLR' with k=1 returns 4 instead of 5. The sliding window approach only tracks cumulative position changes at specific iterations rather than computing the final position after each independent k-length substring removal.
To fix, either explicitly remove each substring and compute final positions, or precompute prefix/suffix sums to calculate O(1) effects for each of the (len(s) - k + 1) possible removals.
🤖 Prompt for AI Agents
In solutions/3694/01.py around lines 6 to 29, the sliding-window mutating of x,y
is incorrect because it tracks incremental changes rather than computing the
final position after independently removing each k-length substring; fix by
computing prefix displacements and using them to get each removal's final
position in O(1): build pos array where pos[i] is (x,y) after the first i
characters, let total = pos[n], then for each removal start i in [0..n-k]
compute final = pos[i] + (total - pos[i+k]) and add final to seen;
alternatively, if you prefer simplicity, explicitly simulate removing each
substring by concatenating s[:i] + s[i+k:] and computing its final displacement,
but the prefix approach is preferred for O(n).
| class Solution: | ||
| def splitArray(self, nums: List[int]) -> int: |
There was a problem hiding this comment.
Add missing import for type hints.
The List type hint is used but not imported, causing a NameError at runtime when type hints are evaluated.
🔎 Proposed fix
+from typing import List
+
class Solution:
def splitArray(self, nums: List[int]) -> int:📝 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.
| class Solution: | |
| def splitArray(self, nums: List[int]) -> int: | |
| from typing import List | |
| class Solution: | |
| def splitArray(self, nums: List[int]) -> int: |
🧰 Tools
🪛 Ruff (0.14.8)
2-2: Undefined name List
(F821)
🤖 Prompt for AI Agents
In solutions/3698/01.py around lines 1 to 2, the type hint List is referenced
but not imported, causing a NameError; fix by adding the missing import
statement from the typing module (from typing import List) at the top of the
file so the List type hint is defined, or alternatively change the annotation to
use built-in list if targeting Python 3.9+.
romankurnovskii
deleted the
problems-3705-3698-3694-3690-3675-3653-3649-3648-3645-3644-3643
branch
2 participants
Summary
This PR adds solutions and explanations for 10 LeetCode problems. All solutions were developed after reviewing community solutions and best practices using MCP tools.
Problems Solved
Problem 3643: Flip Square Submatrix Vertically (Easy)
Problem 3644: Maximum K to Sort a Permutation (Medium)
Problem 3645: Maximum Total from Optimal Activation Order (Medium)
Problem 3648: Minimum Sensors to Cover Grid (Medium)
Problem 3649: Number of Perfect Pairs (Medium)
Problem 3653: XOR After Range Multiplication Queries I (Medium)
Problem 3675: Minimum Operations to Transform String (Medium)
Problem 3690: Split and Merge Array Transformation (Medium)
Problem 3694: Distinct Points Reachable After Substring Removal (Medium)
Problem 3698: Split Array With Minimum Difference (Medium)
Changes
Note
Problem 3705 (Find Golden Hour Customers) already had a solution in the repository, so it was not included in this PR.
Summary by Sourcery
Add Python solutions and accompanying explanations for several LeetCode-style problems involving matrix manipulation, permutation sorting constraints, range multiplication with XOR aggregation, grid coverage, pair counting, string transformation, BFS-based array transformations, substring-removal path counting, and mountain-array splitting.
New Features:
Documentation:
Summary by CodeRabbit
New Features
Documentation
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