Add solutions and explanations for problems 27, 156, 157, 158, 159, 161, 163, 170 #109
Conversation
![sourcery-ai[bot]](https://avatars.githubusercontent.com/in/48477?s=60&v=4){kind=small}
There was a problem hiding this comment.
Sorry @vikahaze, your pull request is larger than the review limit of 150000 diff characters
|
Caution Review failedThe pull request is closed. WalkthroughAdds many new explanation markdowns and Python solution files, expands the book documentation with numerous LeetCode problem entries, converts one solution function into a class method, and applies several script/JSON serialization updates including premium-aware filtering in a normalization script. Changes
Estimated code review effort🎯 3 (Moderate) | ⏱️ ~25 minutes
Possibly related PRs
Pre-merge checks and finishing touches❌ Failed checks (1 warning)
✅ Passed checks (2 passed)
📜 Recent review detailsConfiguration used: CodeRabbit UI Review profile: CHILL Plan: Pro 📒 Files selected for processing (6)
Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out. Comment |
![coderabbitai[bot]](https://avatars.githubusercontent.com/in/347564?s=60&v=4){kind=small}
There was a problem hiding this comment.
Actionable comments posted: 2
🧹 Nitpick comments (6)
solutions/163/01.py (1)
4-15: LGTM! Consider unpacking syntax for style consistency.The algorithm correctly identifies missing ranges by checking gaps between numbers. The approach of appending
upper + 1to handle the final range is elegant.For slightly more Pythonic code, consider using unpacking:
- for num in nums + [upper + 1]: + for num in [*nums, upper + 1]:This is a minor style preference mentioned by the linter and doesn't affect functionality.
solutions/158/01.py (1)
7-24: LGTM! Correct buffering approach for multiple calls.The solution properly handles multiple read calls by:
- Maintaining an internal queue to buffer leftover characters
- Consuming buffered characters before calling read4
- Adding new characters from read4 to the buffer
- Stopping at EOF or when n characters are read
The static analysis warning about
read4is a false positive—it's provided by the LeetCode platform.For slightly better performance, consider using
collections.dequeinstead of a list for the queue, sincepop(0)on a list is O(n). However, given the queue holds at most 4 elements, the current implementation is acceptable:+from collections import deque + class Solution: def __init__(self): - self.queue = [] + self.queue = deque() def read(self, buf: List[str], n: int) -> int: idx = 0 while idx < n: if self.queue: - buf[idx] = self.queue.pop(0) + buf[idx] = self.queue.popleft() idx += 1 else: buf4 = [''] * 4 count = read4(buf4) if count == 0: break self.queue.extend(buf4[:count]) return idxbooks/All.md (4)
4303-4321: Remove stray__init__stub; keep solution block minimal.The
def __init__placeholder before the actual solution is commented-out and unrelated to the algorithm. It distracts readers and may confuse tooling that extracts code. Please remove it and keep only the solution function.Apply this edit to streamline the snippet:
-```python -def __init__(self, val=0, left=None, right=None): -# self.val = val -# self.left = left -# self.right = right - -class Solution: +```python +class Solution: def upsideDownBinaryTree(self, root: Optional[TreeNode]) -> Optional[TreeNode]: if not root or not root.left: return root new_root = self.upsideDownBinaryTree(root.left) root.left.left = root.right root.left.right = root root.left = None root.right = None return new_root
6892-6914: Add missing typing import or drop hints; also remove unrelated__init__stub.This snippet uses
Optional[ListNode]but doesn’t importOptional. Either importOptionalor remove the type hints to keep the example simple. Also, thedef __init__stub is unrelated.Minimal, self-contained edit:
-```python -def __init__(self, val=0, next=None): -# self.val = val -# self.next = next -class Solution: +```python +from typing import Optional + +class Solution: def oddEvenList(self, head: Optional[ListNode]) -> Optional[ListNode]: if not head or not head.next: return head odd = head even = head.next even_head = even while even and even.next: odd.next = even.next odd = odd.next even.next = odd.next even = even.next odd.next = even_head return head
8075-8090: Clean up stubs and ensure typing context forTreeNode/Optional.Both “Search in a BST” (lines 8075–8090) and “Insert into a BST” (lines 8180–8199) contain the same commented
__init__stub and useOptionalwithout a local import. For consistency across the book:
- Remove the
def __init__placeholder.- Add
from typing import Optionalat the top of each code block or remove the type hints.Example for 700:
-```python -def __init__(self, val=0, left=None, right=None): -# self.val = val -# self.left = left -# self.right = right -class Solution: +```python +from typing import Optional + +class Solution: def searchBST(self, root: Optional[TreeNode], val: int) -> Optional[TreeNode]: if not root: return None if root.val == val: return root elif root.val > val: return self.searchBST(root.left, val) else: return self.searchBST(root.right, val)Also applies to: 8180-8199
4240-4244: Resolve markdownlint issues: duplicate headings and bare URLs.Multiple new sections repeat “## Explanation” immediately after an “### Explanation” (MD024) and use bare URLs (MD034). This hurts document navigation and link rendering.
- Keep a single “### Strategy” and a single “### Steps” under one “### Explanation”.
- Convert all plain URLs to
[Problem link](...).- Consider adding a pre-commit hook to run markdownlint.
Example hook (optional):
+#!/bin/sh +FILES=$(git diff --cached --name-only --diff-filter=ACM | grep -E '\.md$') +[ -z "$FILES" ] && exit 0 +npx markdownlint-cli2 $FILES || exit 1Also applies to: 4420-4424, 6826-6830, 7187-7191, 7757-7761, 8013-8017, 8544-8548, 8659-8663, 8990-8994, 9570-9574, 9854-9858, 9990-9994
📜 Review details
Configuration used: CodeRabbit UI
Review profile: CHILL
Plan: Pro
📒 Files selected for processing (16)
books/All.md(12 hunks)explanations/156/en.md(1 hunks)explanations/157/en.md(1 hunks)explanations/158/en.md(1 hunks)explanations/159/en.md(1 hunks)explanations/161/en.md(1 hunks)explanations/163/en.md(1 hunks)explanations/170/en.md(1 hunks)explanations/27/en.md(1 hunks)solutions/156/01.py(1 hunks)solutions/157/01.py(1 hunks)solutions/158/01.py(1 hunks)solutions/159/01.py(1 hunks)solutions/161/01.py(1 hunks)solutions/163/01.py(1 hunks)solutions/170/01.py(1 hunks)
🧰 Additional context used
🧬 Code graph analysis (2)
solutions/158/01.py (1)
solutions/157/01.py (2)
Solution(6-20)read(7-20)
solutions/170/01.py (1)
solutions/1/01.js (1)
complement(4-4)
🪛 LanguageTool
explanations/161/en.md
[style] ~14-~14: This phrasing could be wordy, so try replacing it with something more concise.
Context: ...We first check if the length difference is more than 1 (impossible to be one edit). Then we ...
(MORE_THAN_EXCEEDS)
[style] ~24-~24: This phrasing could be wordy, so try replacing it with something more concise.
Context: ...sition:** 1. Check if length difference is more than 1 - if so, return False 2. Ensure s is ...
(MORE_THAN_EXCEEDS)
🪛 markdownlint-cli2 (0.18.1)
books/All.md
4240-4240: Bare URL used
(MD034, no-bare-urls)
4244-4244: Multiple headings with the same content
(MD024, no-duplicate-heading)
4418-4418: Bare URL used
(MD034, no-bare-urls)
4422-4422: Multiple headings with the same content
(MD024, no-duplicate-heading)
6824-6824: Bare URL used
(MD034, no-bare-urls)
6828-6828: Multiple headings with the same content
(MD024, no-duplicate-heading)
7185-7185: Bare URL used
(MD034, no-bare-urls)
7189-7189: Multiple headings with the same content
(MD024, no-duplicate-heading)
7755-7755: Bare URL used
(MD034, no-bare-urls)
7759-7759: Multiple headings with the same content
(MD024, no-duplicate-heading)
8011-8011: Bare URL used
(MD034, no-bare-urls)
8015-8015: Multiple headings with the same content
(MD024, no-duplicate-heading)
8093-8093: Bare URL used
(MD034, no-bare-urls)
8202-8202: Bare URL used
(MD034, no-bare-urls)
8206-8206: Multiple headings with the same content
(MD024, no-duplicate-heading)
8542-8542: Bare URL used
(MD034, no-bare-urls)
8546-8546: Multiple headings with the same content
(MD024, no-duplicate-heading)
8612-8612: Reference links and images should use a label that is defined
Missing link or image reference definition: "0"
(MD052, reference-links-images)
8613-8613: Reference links and images should use a label that is defined
Missing link or image reference definition: "0"
(MD052, reference-links-images)
8657-8657: Bare URL used
(MD034, no-bare-urls)
8661-8661: Multiple headings with the same content
(MD024, no-duplicate-heading)
8988-8988: Bare URL used
(MD034, no-bare-urls)
8992-8992: Multiple headings with the same content
(MD024, no-duplicate-heading)
9568-9568: Bare URL used
(MD034, no-bare-urls)
9572-9572: Multiple headings with the same content
(MD024, no-duplicate-heading)
9852-9852: Bare URL used
(MD034, no-bare-urls)
9856-9856: Multiple headings with the same content
(MD024, no-duplicate-heading)
9988-9988: Bare URL used
(MD034, no-bare-urls)
9992-9992: Multiple headings with the same content
(MD024, no-duplicate-heading)
🪛 Ruff (0.14.7)
solutions/156/01.py
11-11: Undefined name TreeNode
(F821)
11-11: Undefined name TreeNode
(F821)
solutions/163/01.py
8-8: Consider [*nums, upper + 1] instead of concatenation
Replace with [*nums, upper + 1]
(RUF005)
solutions/158/01.py
19-19: Undefined name read4
(F821)
solutions/157/01.py
12-12: Undefined name read4
(F821)
🔇 Additional comments (18)
explanations/161/en.md (1)
1-62: LGTM! Clear and comprehensive explanation.The documentation effectively covers the one-edit-distance problem with accurate complexity analysis, clear decomposition, and helpful trace walkthroughs. The examples demonstrate both true and false cases well.
explanations/27/en.md (1)
1-54: LGTM! Enhanced documentation structure.The updates significantly improve the explanation with better organization, detailed complexity analysis, and a helpful trace table. The distinction between brute force and optimized approaches adds educational value.
solutions/157/01.py (1)
7-20: LGTM! Clean implementation of the read API.The solution correctly handles all edge cases:
- Stops when reaching n characters
- Handles EOF (when read4 returns 0)
- Properly limits copying using
min(count, n - total)- Efficient slice assignment for copying
The static analysis warning about
read4being undefined is a false positive—it's provided by the LeetCode platform as indicated by the comment on lines 3-4.solutions/159/01.py (1)
4-22: LGTM! Correct sliding window implementation.The solution properly implements the sliding window technique:
- Expands the window by adding characters and updating counts
- Shrinks the window when exceeding two distinct characters
- Correctly removes zero-count entries to maintain accurate distinct count
- Tracks the maximum valid window size
The algorithm handles all edge cases correctly and achieves O(n) time complexity.
explanations/159/en.md (1)
1-58: LGTM! Thorough explanation with detailed trace.The documentation effectively explains the sliding window approach with:
- Accurate complexity analysis (O(n) time, O(1) space for at most 2 distinct chars)
- Clear decomposition of the algorithm
- Detailed trace table showing multiple shrink steps
- Good comparison between brute force and optimized approaches
The trace walkthrough with sub-steps (3a, 3b, 4a) is particularly helpful for understanding the window shrinking behavior.
explanations/170/en.md (1)
1-63: LGTM! Clear explanation of the Two Sum data structure.The documentation effectively covers the data structure design with:
- Accurate complexity analysis (O(1) for add, O(n) for find)
- Clear explanation of the hash map frequency approach
- Proper handling of the edge case where complement equals the number
- Detailed trace showing both successful and unsuccessful find operations
- Good comparison between brute force and optimized approaches
The step-by-step walkthrough clearly demonstrates how the hash map enables efficient lookups and handles the special case of duplicate numbers.
solutions/156/01.py (2)
1-9: LGTM! Standard LeetCode pattern.The commented TreeNode definition and undefined type warning from Ruff are expected in LeetCode solutions—the platform provides TreeNode at runtime.
10-22: LGTM! Correct recursive transformation.The implementation correctly handles the upside-down transformation: base case guards against empty/leaf nodes, recursion finds the new root, and pointer reassignments during backtracking establish the transformed structure.
solutions/170/01.py (3)
1-5: LGTM! Clean initialization.Using
defaultdict(int)is appropriate for tracking element frequencies.
7-8: LGTM! Correct add implementation.The method efficiently tracks element frequencies in O(1) time.
10-16: LGTM! Correct two-sum logic.The implementation correctly handles both distinct-number pairs and same-number pairs (requiring count > 1). The logic is sound and matches the problem requirements.
explanations/163/en.md (1)
1-57: LGTM! Clear and well-structured explanation.The documentation follows the template with comprehensive strategy breakdown, complexity analysis, and an effective trace table for understanding the algorithm.
solutions/161/01.py (3)
1-10: LGTM! Efficient guard and normalization.The length-difference guard (lines 5-6) and swap normalization (lines 8-10) correctly handle impossible cases and simplify the subsequent logic.
12-17: LGTM! Correct mismatch handling.The logic correctly distinguishes between replacement (same length) and insertion/deletion (different length) by comparing the appropriate substrings.
19-19: LGTM! Correct no-mismatch handling.When no mismatch is found within
s's range, the function correctly returnsTrueonly ifthas exactly one additional character, ensuring exactly one edit distance.explanations/158/en.md (1)
1-63: LGTM! Clear explanation of stateful buffering.The documentation effectively explains the key difference from problem 157: maintaining a queue to preserve leftover characters between multiple calls. The trace table clearly demonstrates the buffering behavior.
explanations/157/en.md (1)
1-54: LGTM! Clear explanation of batched reading.The documentation effectively explains the strategy of reading in chunks of 4 and handling partial reads. The trace table clearly shows how the buffer is filled across iterations.
explanations/156/en.md (1)
1-56: LGTM! Excellent explanation of recursive transformation.The documentation clearly explains the upside-down transformation with effective use of the trace table to show both the recursive descent and backtracking pointer reassignments. Well aligned with the code implementation.
| def __init__(self): | ||
| self.num_counts = defaultdict(int) | ||
| def add(self, number: int) -> None: | ||
| self.num_counts[number] += 1 | ||
| def find(self, value: int) -> bool: | ||
| for num in self.num_counts: | ||
| complement = value - num | ||
| if complement in self.num_counts: | ||
| if complement != num or self.num_counts[num] > 1: | ||
| return True | ||
| return False | ||
| ``` |
There was a problem hiding this comment.
Missing import for defaultdict (code won’t run as-is).
defaultdict is used but never imported. Add the import to make the snippet self-contained.
Apply this fix:
-```python
-def __init__(self):
- self.num_counts = defaultdict(int)
+```python
+from collections import defaultdict
+
+def __init__(self):
+ self.num_counts = defaultdict(int)
def add(self, number: int) -> None:
self.num_counts[number] += 1
def find(self, value: int) -> bool:
for num in self.num_counts:
complement = value - num
if complement in self.num_counts:
if complement != num or self.num_counts[num] > 1:
return True
return False🤖 Prompt for AI Agents
In books/All.md around lines 4488 to 4501 the snippet uses defaultdict but never
imports it; add "from collections import defaultdict" at the top of the snippet
(before __init__) so the class can instantiate defaultdict(int) and the code
runs as-is.
| https://leetcode.com/problems/leaf-similar-trees/ | ||
|
|
||
| ### Explanation | ||
|
|
||
| ## Explanation | ||
|
|
||
| ### Strategy (The "Why") | ||
|
|
||
| **1.1 Constraints & Complexity:** | ||
|
|
||
| * **Input Size:** Each tree can have up to 200 nodes. | ||
| * **Time Complexity:** O(n + m) - We traverse both trees once to collect leaves, where n and m are the number of nodes in each tree. | ||
| * **Space Complexity:** O(n + m) - We store leaf sequences for both trees, plus O(h) for recursion stack. | ||
| * **Edge Case:** If both trees are empty, they are leaf-similar (both have empty leaf sequences). | ||
|
|
||
| **1.2 High-level approach:** |
There was a problem hiding this comment.
🧩 Analysis chain
🏁 Script executed:
#!/bin/bash
# Check if markdownlint-cli2 is available, install if needed
if ! command -v npx &> /dev/null; then
echo "npx not available, attempting to install Node.js packages..."
npm install -g markdownlint-cli2 2>&1 | head -20
fi
# Run markdownlint on the file
npx markdownlint-cli2 books/All.md 2>&1 | head -100Repository: romankurnovskii/leetcode-apps
Length of output: 9644
🏁 Script executed:
#!/bin/bash
# Also inspect the actual file content around lines 8202-8217 to confirm the issues
sed -n '8195,8225p' books/All.md | cat -nRepository: romankurnovskii/leetcode-apps
Length of output: 1387
🏁 Script executed:
#!/bin/bash
# Search for the pattern of duplicate headings throughout the file to assess scope
rg '### Explanation\s+## Explanation' books/All.md --multiline -A 2 -B 2 | head -50Repository: romankurnovskii/leetcode-apps
Length of output: 840
Replace bare URL with Markdown link and deduplicate headings.
The bare URL (line 8202) should be converted to a Markdown link, and the duplicate "### Explanation" / "## Explanation" headings (lines 8204-8206) should be consolidated to a single "### Explanation". This pattern—bare URLs followed by duplicated "Explanation" headings—appears throughout the file and should be standardized consistently.
Example fix for this section:
-## 872. Leaf-Similar Trees [Easy]
-https://leetcode.com/problems/leaf-similar-trees/
+## 872. Leaf-Similar Trees [Easy]
+[Problem link](https://leetcode.com/problems/leaf-similar-trees/)
-
-### Explanation
-
-## Explanation
+### ExplanationMarkdownlint identifies 2502 formatting errors in All.md, including bare URLs (MD034), duplicate headings (MD024), and structural inconsistencies. A full lint pass should be run to address all formatting issues systematically.
Committable suggestion skipped: line range outside the PR's diff.
🧰 Tools
🪛 markdownlint-cli2 (0.18.1)
8202-8202: Bare URL used
(MD034, no-bare-urls)
8206-8206: Multiple headings with the same content
(MD024, no-duplicate-heading)
… 27 solution format
There was a problem hiding this comment.
Actionable comments posted: 1
🧹 Nitpick comments (2)
scripts/normalize_book_sets.py (2)
121-135: Accumulate premium problems instead of overwritingpremium_setInside the loop,
premium_setis reassigned for each object with apremiumfield, so only the last such object contributes. Ifbook-sets.jsonever contains multiple premium lists, earlier ones would be silently ignored. Prefer accumulating:- premium_set = set() + premium_set = set() @@ - elif "premium" in obj: - # Get premium problems list - premium_set = set(obj.get("premium", [])) + elif "premium" in obj: + # Accumulate premium problems from any object + premium_set |= set(obj.get("premium", []))This is backward‑compatible even if there is only one premium section today.
137-169: All-TODO premium filtering logic is good; consider updating the high-level docsThe updated All-TODO handling correctly:
- strips out premium problems via
removed_premium, and- separately removes problems that already have both solution and explanation.
That matches the intent of keeping a non‑premium, unsolved backlog. However, the module docstring at the top still only mentions removing problems that have both solution and explanation; it doesn’t mention premium-based removals. Consider updating that docstring (and optionally the CLI description) to mention premium exclusion so future readers aren’t surprised by this behavior.
📜 Review details
Configuration used: CodeRabbit UI
Review profile: CHILL
Plan: Pro
📒 Files selected for processing (2)
scripts/normalize_book_sets.py(3 hunks)solutions/27/01.py(1 hunks)
🧰 Additional context used
🪛 Ruff (0.14.7)
scripts/normalize_book_sets.py
159-159: f-string without any placeholders
Remove extraneous f prefix
(F541)
🔇 Additional comments (2)
solutions/27/01.py (1)
4-15: LGTM! Clean refactoring with correct two-pointer implementation.The refactoring to a class-based interface follows LeetCode conventions perfectly. The two-pointer algorithm is correctly implemented:
- The slow pointer tracks where to place the next non-val element
- The fast pointer scans through the array
- In-place modification with O(n) time and O(1) space complexity
The logic handles all edge cases correctly (empty array, all elements equal to val, no matching elements).
scripts/normalize_book_sets.py (1)
187-197: Premium exclusion from “All” set looks correctThe list comprehension for
problems_with_bothnow correctly:
- restricts to problems that have both solution and explanation, and
- excludes any problem numbers present in
premium_set.This matches the intended behavior of keeping premium problems out of the “All” set while preserving the existing constraints. No changes needed here.
…All and All-TODO sets
…manual formatting
There was a problem hiding this comment.
Actionable comments posted: 0
♻️ Duplicate comments (1)
scripts/normalize_book_sets.py (1)
281-301: Remove unnecessary f-string on the “[All] Updating problem list” logRuff correctly flags an f-string without placeholders at Line 287:
print(f"\n[All] Updating problem list:")It should be a plain string:
- print(f"\n[All] Updating problem list:") + print("\n[All] Updating problem list:")This clears F541 and matches how other static messages are printed.
🧹 Nitpick comments (3)
scripts/normalize_book_sets.py (3)
20-99: Consider wiringcompact_json_arraysinto the JSON write pathThe
compact_json_arrayshelper looks solid for compacting numeric arrays, but it is currently unused. As written, future runs of this script will fall back to plainjson.dump, potentially losing your desired formatting.If you want this normalization to be stable and automatic, consider updating the write block to use the helper:
- try: - with open(book_sets_file, "w", encoding="utf-8") as f: - json.dump(data, f, indent=2, ensure_ascii=False) + try: + with open(book_sets_file, "w", encoding="utf-8") as f: + json_str = json.dumps(data, indent=2, ensure_ascii=False) + f.write(compact_json_arrays(json_str))This keeps
book-sets.jsonconsistently normalized whenever the script runs.
204-216:premium_setonly reflects the last object with a"premium"keyIn the discovery loop (around Line 214),
premium_setis reassigned each time an object with a"premium"field is seen:elif "premium" in obj: premium_set = set(obj.get("premium", []))If
book-sets.jsonever contains multiple such objects, earlier premium lists will be silently overwritten. If the intent is to treat all of them as premium, consider accumulating instead:- elif "premium" in obj: - # Get premium problems list - premium_set = set(obj.get("premium", [])) + elif "premium" in obj: + # Accumulate premium problems from all premium-aware sets + premium_set |= set(obj.get("premium", []))If you are certain there will always be exactly one such object, this is fine as-is; otherwise, the union form is safer.
384-387: Writing JSON ignorescompact_json_arraysformattingThe final write block still uses
json.dump, which will produce the default “one number per line” arrays and ignore your new compaction logic. If the goal is to keepbook-sets.jsonnormalized with compact numeric arrays, please update this block as suggested in the earlier comment so the helper is actually applied.
📜 Review details
Configuration used: CodeRabbit UI
Review profile: CHILL
Plan: Pro
📒 Files selected for processing (1)
scripts/normalize_book_sets.py(5 hunks)
🧰 Additional context used
🪛 Ruff (0.14.7)
scripts/normalize_book_sets.py
287-287: f-string without any placeholders
Remove extraneous f prefix
(F541)
2 participants
Summary
This PR adds solutions and explanations for 8 LeetCode problems following the standardized template format.
Problems Added
Changes
Normalization
data/book-sets.jsonto include new problems in "All" setSummary by CodeRabbit
Documentation
New Features
Refactor
Chores
✏️ Tip: You can customize this high-level summary in your review settings.