chore: add validation for dna sequences

Author: BrianLusina

algorithms/sliding_window/repeated_dna_sequences/__init__.py

@@ -42,6 +42,11 @@ def find_repeated_dna_sequences(dna_sequence: str) -> List[str]:
         List[str]
     """
     to_int = {"A": 0, "C": 1, "G": 2, "T": 3}
+
+     # Validate input contains only valid DNA bases
+    if not all(c in to_int for c in dna_sequence):
+        raise ValueError(f"DNA sequence contains invalid characters. Only A, C, G, T are allowed.")
+
     encoded_sequence = [to_int[c] for c in dna_sequence]
 
     dna_sequence_substr_length, dna_sequence_length = 10, len(dna_sequence) # Length of DNA sequence to check