Merge pull request #13 from codewithme-py/feat/generate-parentheses-0022

problem solution & test 0022 + chore: fix makefile

Author: codewithme-py

Makefile

@@ -1,8 +1,10 @@
 .PHONY: problem
 problem:
-	@if [ -z '$(filter-out problem,$(MAKECMDGOALS))']; then \
+	@if [ -z '$(filter-out problem,$(MAKECMDGOALS))' ]; then \
 		echo 'Usage: make problem <problem_number>'; \
 		exit 1; \
 	fi
 	@uv run scripts/create_problem.py $(filter-out problem,$(MAKECMDGOALS))
-	
+
+%:
+	@:

solutions/generate_parentheses_0022.py

@@ -0,0 +1,33 @@
+class Solution:
+    def generateParenthesis(self, n: int) -> list[str]:
+        """
+        Generate all valid combinations of n pairs of parentheses.
+
+        Uses backtracking: build combinations by adding '(' or ')'
+        until the length reaches 2*n.
+
+        Validity rules:
+        - '(' can be added if open_count < n
+        - ')' can be added if close_count < open_count
+
+        Args:
+            n: Number of pairs of parentheses (1 <= n <= 8)
+
+        Returns:
+            List of all valid combinations of parentheses
+
+        Time Complexity: O(4^n / sqrt(n)) - Catalan number
+        Space Complexity: O(n) - recursion depth
+        """
+        open_bracket, close_bracket = '(', ')'
+        result: list[str] = []
+        def backtrack(current: str, open_count: int, close_count: int) -> None:
+            if len(current) == n * 2:
+                result.append(current)
+                return
+            if open_count < n:
+                backtrack(current + open_bracket, open_count + 1, close_count)
+            if close_count < open_count:
+                backtrack(current + close_bracket, open_count, close_count + 1)
+        backtrack('', 0, 0)
+        return result

tests/test_generate_parentheses_0022.py

@@ -0,0 +1,13 @@
+import pytest
+
+from solutions.generate_parentheses_0022 import Solution
+
+
+@pytest.mark.parametrize('n, expected', [
+    (1, ['()']),
+    (2, ['(())', '()()']),
+    (3, ['((()))', '(()())', '(())()', '()(())', '()()()']),
+])
+def test_solution(n: int, expected: list[str]) -> None:
+    sol = Solution()
+    assert sol.generateParenthesis(n) == expected