feat(day 135): count email reply and forward markers using case-insensitive regex

Author: JohnSunny21

FreeCodeCamp/CodingQ/ReFwdFwCount.py

@@ -0,0 +1,92 @@
+"""  
+Re: Fwd: Fw: Count
+Given a string representing the subject line of an email, determine how many times the email has been forwarded or replied to.
+
+For simplicity, consider an email forwarded or replied to if the string contains any of the following markers (case-insensitive):
+
+"fw:"
+"fwd:"
+"re:"
+Return the total number of occurrences of these markers.
+
+
+"""
+import unittest
+
+class ReFwdFwCountTest(unittest.TestCase):
+
+    def test1(self):
+        self.assertEqual(email_chain_count("Re: Meeting Notes"), 1)
+
+    def test2(self):
+        self.assertEqual(email_chain_count("Meeting Notes"), 0)
+    
+    def test3(self):
+        self.assertEqual(email_chain_count("Re: re: RE: rE: Meeting Notes"), 4)
+
+    def test4(self):
+        self.assertEqual(email_chain_count("Re: Fwd: Re: Fw: Re: Meeting Notes"), 5)
+
+    def test5(self):
+        self.assertEqual(email_chain_count("re:Ref:fw:re:review:FW:Re:fw:report:Re:FW:followup:re:summary:Fwd:Re:fw:NextStep:RE:FW:re:Project:Fwd:Re:fw:Notes:RE:re:Update:FWD:Re:fw:Summary"), 23)
+
+
+
+def email_chain_count(subject):
+    subject = subject.lower()
+    checkers = ["fw:","fwd:","re:"]
+    count = 0
+    for check in checkers:
+        count += subject.count(check)
+    
+    return count
+
+"""  
+The above solution works fine for some cases but there are issues with this code
+
+1. Overlapping markers
+    -> "fwd:" contains "fw:"
+    -> if the subject has "fwd:", the above code will count both "fw:" and "fwd:"
+    Example:
+        print(email_chain_count("Fwd: Meetig"))
+        # Output: 2 (counts "fw:" and "fwd:")
+
+        # Expected: 1
+
+2. Exact matching:
+    -> if you want to avoid double-counting, you need to ensure "fw:" and "fwd:" are treated as distinct
+        tokens, not substrings.
+
+=> This solution works fine unless "fwd:" appears, where it double-count because "fw:" is a substring of "fwd:".
+=> Regex avoids this overlap by treating each marker as a distinct option.
+=> if the requirement is okay with the slight overcount, this version is perfectly serviceable. If you want exact correctness,
+regext is the safer choice.
+
+"""
+
+import re
+# Corrected Version
+def email_chain_count(subject):
+
+    markers = ["fw:","fwd:","re:"]
+
+    pattern = re.compile(r"(fw:|fwd:|re:)",re.IGNORECASE)
+
+    matches = pattern.findall(subject)
+
+    return len(matches)
+
+"""  
+This solution
+
+=> Use case-insensitive matching re.IGNORECASE in (python, /gi i JS).
+=> Regex is the cleanest way since it handles overlapping and mixed cases.
+=> The result is simply the length of all matches.
+
+"""
+
+
+
+if __name__ == "__main__":
+    
+    unittest.main()