Changed code

Author: Casey1022

rounds/3_dna/solution.py

@@ -5,13 +5,37 @@
 own faster implementation.
 """
 
-from .baseline import find_matches as _baseline
+from __future__ import annotations
 
 
 def find_matches(fasta_path: str, pattern: bytes) -> list[tuple[str, list[int]]]:
     """Find every FASTA record whose sequence contains ``pattern``.
 
     Returns ``[(record_id, [positions...]), ...]`` in file order.
     """
-    # TODO: remove this delegation and write your own implementation here.
-    return _baseline(fasta_path, pattern)
+    with open(fasta_path, "rb") as f:
+        text = f.read()
+
+    matches: list[tuple[str, list[int]]] = []
+
+    for record in text.split(b">"):
+        if not record.strip():
+            continue
+
+        lines = record.split(b"\n")
+        record_id = lines[0].strip().decode("ascii")
+        sequence = b"".join(lines[1:]).replace(b" ", b"")
+
+        positions: list[int] = []
+        start = 0
+        while True:
+            pos = sequence.find(pattern, start)
+            if pos == -1:
+                break
+            positions.append(pos)
+            start = pos + 1
+
+        if positions:
+            matches.append((record_id, positions))
+
+    return matches