| 1 | import itertools |
| 2 | import re |
| 3 | |
| 1 | 4 | def solve(puzzle: str) -> dict[str, int] | None: |
| 2 | | pass |
| 5 | # Edge Case: Empty or None puzzle |
| 6 | if not puzzle: |
| 7 | return None |
| 8 | |
| 9 | # Parse the puzzle into words |
| 10 | # The puzzle is expected to be in the format "A + B == C" or similar |
| 11 | # We extract all uppercase words (potential alphametic words) |
| 12 | words = re.findall(r'[A-Z]+', puzzle) |
| 13 | |
| 14 | # Check if this is an addition puzzle (contains + and ==) |
| 15 | if '+' not in puzzle or '==' not in puzzle: |
| 16 | # For now, we only support addition puzzles |
| 17 | return None |
| 18 | |
| 19 | # Edge Case: No words found in puzzle |
| 20 | if not words: |
| 21 | return None |
| 22 | |
| 23 | # The last word is the result, the rest are addends |
| 24 | addends = words[:-1] |
| 25 | result = words[-1] |
| 26 | |
| 27 | # Edge Case: No addends (e.g., just "A == BC") |
| 28 | if not addends: |
| 29 | return None |
| 30 | |
| 31 | # Get all unique letters |
| 32 | unique_letters = set(''.join(words)) |
| 33 | |
| 34 | # Edge Case: More than 10 unique letters (impossible to solve with digits 0-9) |
| 35 | if len(unique_letters) > 10: |
| 36 | return None |
| 37 | |
| 38 | # Get first letters of each word (cannot be zero) |
| 39 | first_letters = {word[0] for word in words} |
| 40 | |
| 41 | # Generate all possible digit assignments |
| 42 | digits = range(10) |
| 43 | |
| 44 | # Convert unique_letters to a list for consistent ordering |
| 45 | unique_letters_list = list(unique_letters) |
| 46 | |
| 47 | # Try all permutations of digits for the unique letters |
| 48 | for perm in itertools.permutations(digits, len(unique_letters_list)): |
| 49 | # Create a mapping from letters to digits |
| 50 | mapping = dict(zip(unique_letters_list, perm)) |
| 51 | |
| 52 | # Edge Case: Leading digit is zero |
| 53 | if any(mapping[letter] == 0 for letter in first_letters): |
| 54 | continue |
| 55 | |
| 56 | # Convert words to numbers using the mapping |
| 57 | def word_to_number(word): |
| 58 | return int(''.join(str(mapping[letter]) for letter in word)) |
| 59 | |
| 60 | # Calculate the sum of addends |
| 61 | addend_sum = sum(word_to_number(addend) for addend in addends) |
| 62 | |
| 63 | # Calculate the result value |
| 64 | result_value = word_to_number(result) |
| 65 | |
| 66 | # Check if the equation is satisfied |
| 67 | if addend_sum == result_value: |
| 68 | return mapping |
| 69 | |
| 70 | # Edge Case: No solution found |
| 71 | return None |
| 72 | # Handled Edge Cases: Empty or None puzzle, No words found in puzzle, No addends, More than 10 unique letters, Leading digit is zero, No solution found |