"Regular Expression Matching" solution

Author: lancelote

src/regular_expression_matching.py

@@ -0,0 +1,30 @@
+class Solution:
+    def isMatch(self, s: str, p: str) -> bool:
+        cache: dict[tuple[int, int], bool] = {}
+
+        def dfs(i: int, j: int) -> bool:
+            if (i, j) in cache:
+                return cache[(i, j)]
+
+            if i >= len(s) and j >= len(p):
+                result = True
+            elif i >= len(s) and j < len(p) - 1 and p[j + 1] == "*":
+                result = dfs(i, j + 2)
+            elif i == len(s) or j == len(p):
+                result = False
+            elif j < len(p) - 1 and p[j + 1] == "*":
+                if s[i] == p[j] or p[j] == ".":
+                    result = dfs(i + 1, j) or dfs(i, j + 2)
+                else:
+                    result = dfs(i, j + 2)
+            elif p[j] == ".":
+                result = dfs(i + 1, j + 1)
+            elif s[i] != p[j]:
+                result = False
+            else:
+                result = dfs(i + 1, j + 1)
+
+            cache[(i, j)] = result
+            return result
+
+        return dfs(0, 0)

tests/test_regular_expression_matching.py

@@ -0,0 +1,17 @@
+import pytest
+
+from src.regular_expression_matching import Solution
+
+
+@pytest.mark.parametrize(
+    "s,p,expected",
+    (
+        ("aa", "a", False),
+        ("aa", "a*", True),
+        ("ab", ".*", True),
+        ("a", "a*b*", True),
+        ("aabcbcbcaccbcaabc", ".*a*aa*.*b*.c*.*a*", True),
+    ),
+)
+def test_solution(s, p, expected):
+    assert Solution().isMatch(s, p) is expected