| 1 | 1 | def answer(question: str) -> int: |
| 2 | | pass |
| 2 | # Edge Case: Empty question |
| 3 | if not question: |
| 4 | raise ValueError("syntax error") |
| 5 | |
| 6 | # Edge Case: Question doesn't start with "What is" |
| 7 | if not question.startswith("What is"): |
| 8 | raise ValueError("unknown operation") |
| 9 | |
| 10 | # Remove "What is" prefix and the trailing question mark |
| 11 | expression = question[8:-1].strip() |
| 12 | |
| 13 | # Edge Case: Empty expression after removing prefix and question mark |
| 14 | if not expression: |
| 15 | raise ValueError("syntax error") |
| 16 | |
| 17 | # Tokenize the expression |
| 18 | tokens = [] |
| 19 | i = 0 |
| 20 | while i < len(expression): |
| 21 | if expression[i].isspace(): |
| 22 | i += 1 |
| 23 | continue |
| 24 | elif expression[i].isdigit() or (expression[i] == '-' and i < len(expression) - 1 and expression[i+1].isdigit()): |
| 25 | # Parse number (including negative numbers) |
| 26 | start = i |
| 27 | if expression[i] == '-': |
| 28 | i += 1 |
| 29 | while i < len(expression) and (expression[i].isdigit() or expression[i] == '.'): |
| 30 | i += 1 |
| 31 | # Edge Case: Non-integer numbers |
| 32 | if '.' in expression[start:i]: |
| 33 | raise ValueError("syntax error") |
| 34 | tokens.append(int(expression[start:i])) |
| 35 | elif expression[i:].startswith('plus'): |
| 36 | tokens.append('plus') |
| 37 | i += 4 |
| 38 | elif expression[i:].startswith('minus'): |
| 39 | tokens.append('minus') |
| 40 | i += 5 |
| 41 | elif expression[i:].startswith('multiplied by'): |
| 42 | tokens.append('multiplied') |
| 43 | i += 13 |
| 44 | elif expression[i:].startswith('divided by'): |
| 45 | tokens.append('divided') |
| 46 | i += 10 |
| 47 | else: |
| 48 | # Edge Case: Unknown operations |
| 49 | raise ValueError("unknown operation") |
| 50 | |
| 51 | # Edge Case: Invalid syntax - empty tokens |
| 52 | if not tokens: |
| 53 | raise ValueError("syntax error") |
| 54 | |
| 55 | # Edge Case: Expression starting with an operator |
| 56 | if isinstance(tokens[0], str) and tokens[0] in ['plus', 'minus', 'multiplied', 'divided']: |
| 57 | raise ValueError("syntax error") |
| 58 | |
| 59 | # Evaluate the expression from left to right |
| 60 | result = tokens[0] |
| 61 | i = 1 |
| 62 | while i < len(tokens): |
| 63 | # Edge Case: Consecutive operators |
| 64 | if i+1 >= len(tokens): |
| 65 | raise ValueError("syntax error") |
| 66 | |
| 67 | operator = tokens[i] |
| 68 | operand = tokens[i+1] |
| 69 | |
| 70 | # Edge Case: Non-numeric operand |
| 71 | if not isinstance(operand, int): |
| 72 | raise ValueError("syntax error") |
| 73 | |
| 74 | if operator == 'plus': |
| 75 | result += operand |
| 76 | elif operator == 'minus': |
| 77 | result -= operand |
| 78 | elif operator == 'multiplied': |
| 79 | result *= operand |
| 80 | elif operator == 'divided': |
| 81 | result //= operand # Integer division as per examples |
| 82 | else: |
| 83 | # Edge Case: Unknown operator during evaluation |
| 84 | raise ValueError("unknown operation") |
| 85 | |
| 86 | i += 2 |
| 87 | |
| 88 | return result |
| 89 | # Handled Edge Cases: Empty question, Question doesn't start with "What is", Empty expression after removing prefix and question mark, Non-integer numbers, Unknown operations, Invalid syntax - empty tokens, Expression starting with an operator, Consecutive operators, Non-numeric operand, Unknown operator during evaluation |