Update solver_factorial.py

solver_factorial.py

@@ -8,48 +8,48 @@ from models import SolverResult
 
 
 def solve_factorial(text: str) -> Optional[SolverResult]:
-    lower = (text or "").lower()
+    raw = text or ""
+    lower = raw.lower()
 
-    if "!" not in text and "factorial" not in lower:
+    if "!" not in raw and "factorial" not in lower and "trailing zero" not in lower:
         return None
 
-    # n!
-    m = re.search(r"(\d+)\s*!", text)
+    # trailing zeros in n!
+    m = re.search(r"trailing zeros?.*?(\d+)\s*!", lower)
     if m:
         n = int(m.group(1))
-        if n < 0:
-            return None
-        result = math.factorial(n)
+        count = 0
+        power = 5
+        while power <= n:
+            count += n // power
+            power *= 5
+
         return SolverResult(
             domain="quant",
             solved=True,
-            topic="factorial",
-            answer_value=str(result),
-            internal_answer=str(result),
+            topic="factorial_trailing_zeros",
+            answer_value=str(count),
+            internal_answer=str(count),
             steps=[
-                "Use n! = n × (n−1) × ... × 1.",
+                "Trailing zeros come from factors of 10.",
+                "Each 10 contributes one 2 and one 5.",
+                "In factorials, 5s are the limiting factor, so count factors of 5.",
             ],
         )
 
-    # "how many trailing zeros in 100!"
-    m = re.search(r"trailing zeros.*?(\d+)\s*!", lower)
+    # direct factorial value
+    m = re.search(r"(\d+)\s*!", raw)
     if m:
         n = int(m.group(1))
-        count = 0
-        power = 5
-        while power <= n:
-            count += n // power
-            power *= 5
+        result = math.factorial(n)
         return SolverResult(
             domain="quant",
             solved=True,
-            topic="factorial_trailing_zeros",
-            answer_value=str(count),
-            internal_answer=str(count),
+            topic="factorial",
+            answer_value=str(result),
+            internal_answer=str(result),
             steps=[
-                "Trailing zeros come from factors of 10 = 2×5.",
-                "There are always more 2s than 5s in a factorial.",
-                "Count factors of 5 using n//5 + n//25 + n//125 + ...",
+                "Expand the factorial as descending multiplication.",
             ],
         )