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feat: add Longest Palindrome
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-31
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9 files changed

+242
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‎.amazonq/rules/problem-creation.md‎

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Original file line numberDiff line numberDiff line change
@@ -15,8 +15,8 @@ When user requests a problem by **number** or **name/slug**, the assistant will:
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4. **Create** JSON file in `.templates/leetcode/json/{problem_name}.json`
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5. **Update** Makefile with `PROBLEM ?= {problem_name}`
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6. **Generate** problem structure using `make p-gen`
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7. **Verify** with `make lint` - fix template issues in JSON if possible, or manually fix generated files if template limitations
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8. **Iterate** if JSON fixes: re-run `make p-gen PROBLEM={problem_name} FORCE=1` and `make lint` until passes to ensure reproducibility
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7. **Verify** with `make p-lint` - fix template issues in JSON if possible, or manually fix generated files if template limitations
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8. **Iterate** if JSON fixes: re-run `make p-gen PROBLEM={problem_name} FORCE=1` and `make p-lint` until passes to ensure reproducibility
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## Scraping Commands
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@@ -148,7 +148,10 @@ make p-gen PROBLEM={problem_name} FORCE=1
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# Test specific problem
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make p-test PROBLEM={problem_name}
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# Lint check
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# Lint problem only (faster)
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make p-lint PROBLEM={problem_name}
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# Lint entire project
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make lint
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```
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‎.templates/leetcode/json/longest_palindrome.json‎

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{
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"problem_name": "longest_palindrome",
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"solution_class_name": "Solution",
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"problem_number": "409",
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"problem_title": "Longest Palindrome",
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"difficulty": "Easy",
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"topics": "Hash Table, String, Greedy",
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"tags": ["grind-75"],
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"readme_description": "Given a string `s` which consists of lowercase or uppercase letters, return the length of the longest palindrome that can be built with those letters.\n\nLetters are case sensitive, for example, \"Aa\" is not considered a palindrome.",
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"readme_examples": [
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{
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"content": "```\nInput: s = \"abccccdd\"\nOutput: 7\n```\n**Explanation:** One longest palindrome that can be built is \"dccaccd\", whose length is 7."
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},
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{
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"content": "```\nInput: s = \"a\"\nOutput: 1\n```\n**Explanation:** The longest palindrome that can be built is \"a\", whose length is 1."
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}
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],
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"readme_constraints": "- `1 <= s.length <= 2000`\n- `s` consists of lowercase and/or uppercase English letters only.",
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"readme_additional": "",
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"solution_imports": "",
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"solution_methods": [
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{
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"name": "longest_palindrome",
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"parameters": "s: str",
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"return_type": "int",
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"dummy_return": "0"
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}
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],
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"test_imports": "import pytest\nfrom leetcode_py.test_utils import logged_test\nfrom .solution import Solution",
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"test_class_name": "LongestPalindrome",
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"test_helper_methods": [
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{ "name": "setup_method", "parameters": "", "body": "self.solution = Solution()" }
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],
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"test_methods": [
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{
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"name": "test_longest_palindrome",
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"parametrize": "s, expected",
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"parametrize_typed": "s: str, expected: int",
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"test_cases": "[('abccccdd', 7), ('a', 1), ('Aa', 1), ('aabbcc', 6)]",
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"body": "result = self.solution.longest_palindrome(s)\nassert result == expected"
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}
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],
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"playground_imports": "from solution import Solution",
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"playground_test_case": "# Example test case\ns = 'abccccdd'\nexpected = 7",
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"playground_execution": "result = Solution().longest_palindrome(s)\nresult",
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"playground_assertion": "assert result == expected"
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}

‎Makefile‎

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Original file line numberDiff line numberDiff line change
@@ -1,6 +1,7 @@
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PYTHON_VERSION = 3.13
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PROBLEM ?= longest_palindromic_substring
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PROBLEM ?= longest_palindrome
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FORCE ?= 0
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COMMA := ,
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sync_submodules:
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git submodule update --init --recursive --remote
@@ -19,23 +20,31 @@ assert_setup_dev:
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chmod +x scripts/shared/python/poetry/assert_setup_dev.sh
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./scripts/shared/python/poetry/assert_setup_dev.sh
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lint:
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poetry sort
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npx prettier --write "**/*.{ts,tsx,css,json,yaml,yml,md}"
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poetry run black .
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poetry run isort .
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poetry run nbqa ruff . --nbqa-exclude=".templates" --ignore=F401,F821
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poetry run ruff check . --exclude="**/*.ipynb"
29-
poetry run mypy \
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define lint_target
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poetry run black $(1)
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poetry run isort $(1)
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$(if $(filter .,$(1)), \
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poetry run nbqa ruff . --nbqa-exclude=".templates" --ignore=F401$(COMMA)F821, \
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poetry run nbqa ruff $(1) --ignore=F401$(COMMA)F821)
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poetry run ruff check $(1) --exclude="**/*.ipynb"
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poetry run mypy $(1) \
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--explicit-package-bases \
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--install-types \
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--non-interactive \
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--check-untyped-defs .
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poetry run nbqa isort . --nbqa-exclude=".templates"
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poetry run nbqa mypy . \
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--nbqa-exclude=".templates" \
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--ignore-missing-imports \
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--disable-error-code=name-defined
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--check-untyped-defs
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$(if $(filter .,$(1)), \
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poetry run nbqa isort . --nbqa-exclude=".templates", \
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poetry run nbqa isort $(1))
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$(if $(filter .,$(1)), \
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poetry run nbqa mypy . --nbqa-exclude=".templates" \
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--ignore-missing-imports --disable-error-code=name-defined, \
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poetry run nbqa mypy $(1) --ignore-missing-imports --disable-error-code=name-defined)
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endef
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lint:
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poetry sort
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npx prettier --write "**/*.{ts,tsx,css,json,yaml,yml,md}"
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$(call lint_target,.)
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test:
@@ -46,7 +55,6 @@ test:
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--ignore=.templates \
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--ignore=leetcode/__pycache__
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# Test Problems
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p-test:
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@echo "Testing problem: $(PROBLEM)"
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@if [ ! -d "leetcode/$(PROBLEM)" ]; then \
@@ -55,11 +63,21 @@ p-test:
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fi
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poetry run pytest leetcode/$(PROBLEM)/tests.py -v -s
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# Generate Problem
66+
p-lint:
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@echo "Linting problem: $(PROBLEM)"
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@if [ ! -d "leetcode/$(PROBLEM)" ]; then \
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echo "Error: Problem '$(PROBLEM)' not found in leetcode/ directory"; \
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exit 1; \
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fi
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$(call lint_target,leetcode/$(PROBLEM))
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p-gen:
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@echo "Generating problem: $(PROBLEM)"
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poetry run python .templates/leetcode/gen.py .templates/leetcode/json/$(PROBLEM).json $(if $(filter 1,$(FORCE)),--force)
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p-del:
79+
rm -rf leetcode/$(PROBLEM)
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# Generate All Problems - useful for people who fork this repo
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gen-all-problems:
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@echo "This will DELETE all existing problems and regenerate from JSON templates."
@@ -72,13 +90,3 @@ gen-all-problems:
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echo "Generating: $$problem"; \
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poetry run python .templates/leetcode/gen.py "$$json_file" $(if $(filter 1,$(FORCE)),--force); \
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done
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# Validate Problem - INTERNAL USE ONLY: For cookiecutter template creation/validation
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# Do not use during normal problem solving - only for template development
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p-validate:
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@echo "Validating problem: $(PROBLEM)"
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@if [ ! -d "leetcode/$(PROBLEM)" ]; then \
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echo "Error: Generated problem '$(PROBLEM)' not found. Run: make p-gen PROBLEM=$(PROBLEM)"; \
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exit 1; \
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fi
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poetry run python .amazonq/plan/compare_template_files.py generated --problem=$(PROBLEM)

‎leetcode/longest_palindrome/README.md‎

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# Longest Palindrome
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**Difficulty:** Easy
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**Topics:** Hash Table, String, Greedy
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**Tags:** grind-75
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**LeetCode:** [Problem 409](https://leetcode.com/problems/longest-palindrome/description/)
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## Problem Description
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Given a string `s` which consists of lowercase or uppercase letters, return the length of the longest palindrome that can be built with those letters.
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Letters are case sensitive, for example, "Aa" is not considered a palindrome.
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## Examples
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### Example 1:
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```
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Input: s = "abccccdd"
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Output: 7
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```
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**Explanation:** One longest palindrome that can be built is "dccaccd", whose length is 7.
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### Example 2:
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```
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Input: s = "a"
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Output: 1
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```
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**Explanation:** The longest palindrome that can be built is "a", whose length is 1.
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## Constraints
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- `1 <= s.length <= 2000`
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- `s` consists of lowercase and/or uppercase English letters only.

‎leetcode/longest_palindrome/__init__.py‎

Whitespace-only changes.

‎leetcode/longest_palindrome/playground.ipynb‎

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{
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"cells": [
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{
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"cell_type": "code",
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"execution_count": null,
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"id": "imports",
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"metadata": {},
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"outputs": [],
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"source": [
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"from solution import Solution"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"id": "setup",
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"metadata": {},
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"outputs": [],
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"source": [
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"# Example test case\n",
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"s = \"abccccdd\"\n",
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"expected = 7"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"id": "execute",
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"metadata": {},
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"outputs": [],
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"source": [
32+
"result = Solution().longest_palindrome(s)\nresult"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"id": "test",
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"metadata": {},
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"outputs": [],
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"source": [
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"assert result == expected"
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]
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}
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],
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"metadata": {
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"kernelspec": {
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"display_name": "leetcode-py-py3.13",
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"language": "python",
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"name": "python3"
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},
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"language_info": {
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"codemirror_mode": {
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"name": "ipython",
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"version": 3
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},
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"file_extension": ".py",
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"mimetype": "text/x-python",
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"name": "python",
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"nbconvert_exporter": "python3",
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"pygments_lexer": "ipython3",
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"version": "3.13.7"
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}
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},
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"nbformat": 4,
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"nbformat_minor": 5
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}

‎leetcode/longest_palindrome/solution.py‎

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class Solution:
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# Time: O(n)
3+
# Space: O(1)
4+
def longest_palindrome(self, s: str) -> int:
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char_count: dict[str, int] = {}
6+
for char in s:
7+
char_count[char] = char_count.get(char, 0) + 1
8+
9+
length = 0
10+
has_odd = False
11+
12+
for count in char_count.values():
13+
length += count // 2 * 2
14+
if count % 2 == 1:
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has_odd = True
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17+
return length + (1 if has_odd else 0)

‎leetcode/longest_palindrome/tests.py‎

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import pytest
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from leetcode_py.test_utils import logged_test
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5+
from .solution import Solution
6+
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8+
class TestLongestPalindrome:
9+
def setup_method(self):
10+
self.solution = Solution()
11+
12+
@pytest.mark.parametrize(
13+
"s, expected",
14+
[
15+
("abccccdd", 7),
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("a", 1),
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("Aa", 1),
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("aabbcc", 6),
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("abc", 1),
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("abcdef", 1),
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("aab", 3),
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("aaaa", 4),
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("AaBbCc", 1),
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("civilwartestingwhetherthatnaptionoranynartionsoconceivedandsodedicatedcanlongendure", 73),
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("bananas", 5),
26+
],
27+
)
28+
@logged_test
29+
def test_longest_palindrome(self, s: str, expected: int):
30+
result = self.solution.longest_palindrome(s)
31+
assert result == expected

‎scripts/shared‎

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