feat(day 119): implement consecutive word compression algorithm with proper run-length grouping

Author: JohnSunny21

FreeCodeCamp/CodingQ/StringCompression.py

@@ -0,0 +1,82 @@
+"""
+
+String Compression
+Given a string sentence, return a compressed version of the sentence where consecutive duplicate words are replaced by the word followed with the number of times it repeats in parentheses.
+
+Only consecutive duplicates are compressed.
+Words are separated by single spaces.
+For example, given "yes yes yes please", return "yes(3) please".
+"""
+
+import unittest
+
+class StringCompressionTest(unittest.TestCase):
+
+    def test1(self):
+        self.assertEqual(compress_string("yes yes yes please"), "yes(3) please")
+
+    def test2(self):
+        self.assertEqual(compress_string("I have have have apples"),"I have(3) apples")
+
+    def test3(self):
+        self.assertEqual(compress_string("one one three and to the the the the"),"one(2) three and to the(4)")
+
+    def test4(self):
+        self.assertEqual(compress_string("route route route route route route tee tee tee tee tee tee"),"route(6) tee(6)")
+        
+
+"""
+Expected: "go stop go stop" (no compression, because duplicates aren't consecutive).
+This code compresses non-consecutive duplicates incorrectly.
+
+Issuse:
+1. Global counting instead of consecutive counting.
+    => This code compressing all duplicates, not just consective ones.
+2. Order preservation
+    => Using a dictionary(words) loses the original order of 
+    appearance in python < 3.7. In modern Python dicts preserve insertion order, but it still doesn't capture
+    consecutive runs.
+
+3. Efficiency
+    => sentence.count(word) scans the whole string for each 
+    word -> O(n2) complexity.
+"""
+def compress_string(sentence):
+    words = {}
+    res = ""
+    for word in sentence.split():
+        if word not in words:
+            words[word] = sentence.count(word)
+
+
+    for word, count in words.items():
+        if count > 1:
+            res += f"{word}({count}) "
+        else:
+            res += f"{word} "
+
+    return res.rstrip()
+
+def compress_string(sentence):
+    words = sentence.split()
+    if not words:
+        return ""
+    
+    result = []
+    count = 1
+    
+    for i in range(1, len(words) + 1):
+        if i < len(words) and words[i] == words[i - 1]:
+            count += 1
+        else:
+            if count > 1:
+                result.append(f"{words[i - 1]}({count})")
+            else:
+                result.append(words[i-1])
+            count = 1
+    return " ".join(result)
+
+
+if __name__ == "__main__":
+    print(compress_string("yes yes yes please"))
+    unittest.main()