"Count Number of Homogenous Substrings" solutions

src/count_number_of_homogenous_substrings.py

@@ -0,0 +1,19 @@
+MOD = 10**9 + 7
+
+
+class Solution:
+    def countHomogenous(self, s: str) -> int:
+        result = 0
+        prev = ""
+        curr_stack = 1
+
+        for x in s:
+            if x == prev:
+                curr_stack += 1
+            else:
+                curr_stack = 1
+
+            result += curr_stack
+            prev = x
+
+        return result % MOD

tests/test_count_number_of_homogenous_substrings.py

@@ -0,0 +1,15 @@
+import pytest
+
+from src.count_number_of_homogenous_substrings import Solution
+
+
+@pytest.mark.parametrize(
+    "s,expected",
+    (
+        ("abbcccaa", 13),
+        ("xy", 2),
+        ("zzzzz", 15),
+    ),
+)
+def test_solution(s, expected):
+    assert Solution().countHomogenous(s) == expected