| 1 | 1 | def answer(question: str) -> int: |
| 2 | | pass |
| 2 | """ |
| 3 | Parse and evaluate a simple math word problem. |
| 4 | |
| 5 | Args: |
| 6 | question: A string representing a math word problem |
| 7 | |
| 8 | Returns: |
| 9 | int: The result of the math operation |
| 10 | |
| 11 | Raises: |
| 12 | ValueError: If the question is malformed, contains unknown operations, or is not a math question |
| 13 | """ |
| 14 | # Edge Case: Empty or None input |
| 15 | if not question: |
| 16 | raise ValueError("syntax error") |
| 17 | |
| 18 | # Edge Case: Question doesn't start with "What is" |
| 19 | if not question.startswith("What is"): |
| 20 | raise ValueError("unknown operation") |
| 21 | |
| 22 | # Edge Case: Question is just "What is" with no numbers or operations |
| 23 | if question == "What is": |
| 24 | raise ValueError("syntax error") |
| 25 | |
| 26 | # Remove the "What is " prefix and the trailing question mark |
| 27 | expression = question[8:-1].strip() |
| 28 | |
| 29 | # Edge Case: Empty expression after removing prefix and question mark |
| 30 | if not expression: |
| 31 | raise ValueError("syntax error") |
| 32 | |
| 33 | # Split the expression into tokens |
| 34 | tokens = expression.split() |
| 35 | |
| 36 | # Edge Case: No tokens |
| 37 | if not tokens: |
| 38 | raise ValueError("syntax error") |
| 39 | |
| 40 | # Define operation mappings |
| 41 | operations = { |
| 42 | "plus": "+", |
| 43 | "minus": "-", |
| 44 | "multiplied": "*", |
| 45 | "divided": "/" |
| 46 | } |
| 47 | |
| 48 | # Parse tokens |
| 49 | parsed_tokens = [] |
| 50 | i = 0 |
| 51 | |
| 52 | # Edge Case: Handle malformed expressions during parsing |
| 53 | while i < len(tokens): |
| 54 | token = tokens[i] |
| 55 | |
| 56 | # If token is a number (including negative numbers) |
| 57 | if token.lstrip('-').isdigit(): |
| 58 | parsed_tokens.append(int(token)) |
| 59 | i += 1 |
| 60 | # If token is an operation |
| 61 | elif token in operations: |
| 62 | # Special handling for "multiplied by" and "divided by" |
| 63 | if token == "multiplied" or token == "divided": |
| 64 | # Edge Case: Missing "by" after "multiplied" or "divided" |
| 65 | if i + 1 >= len(tokens) or tokens[i + 1] != "by": |
| 66 | raise ValueError("syntax error") |
| 67 | parsed_tokens.append(operations[token]) |
| 68 | i += 2 # Skip both the operation and "by" |
| 69 | else: |
| 70 | parsed_tokens.append(operations[token]) |
| 71 | i += 1 |
| 72 | else: |
| 73 | # Edge Case: Unknown operation or invalid token |
| 74 | raise ValueError("unknown operation") |
| 75 | |
| 76 | # Edge Case: Expression starts with an operation |
| 77 | if len(parsed_tokens) > 0 and isinstance(parsed_tokens[0], str): |
| 78 | raise ValueError("syntax error") |
| 79 | |
| 80 | # Edge Case: Expression ends with an operation |
| 81 | if len(parsed_tokens) > 0 and isinstance(parsed_tokens[-1], str): |
| 82 | raise ValueError("syntax error") |
| 83 | |
| 84 | # Edge Case: Even number of tokens (should be odd: number, operation, number, ...) |
| 85 | if len(parsed_tokens) % 2 == 0: |
| 86 | raise ValueError("syntax error") |
| 87 | |
| 88 | # Evaluate the expression from left to right |
| 89 | result = parsed_tokens[0] |
| 90 | |
| 91 | # Edge Case: Handle division by zero |
| 92 | for i in range(1, len(parsed_tokens), 2): |
| 93 | operation = parsed_tokens[i] |
| 94 | operand = parsed_tokens[i + 1] |
| 95 | |
| 96 | # Edge Case: Two consecutive numbers without operation |
| 97 | if not isinstance(operation, str): |
| 98 | raise ValueError("syntax error") |
| 99 | |
| 100 | # Edge Case: Two consecutive operations |
| 101 | if not isinstance(operand, int): |
| 102 | raise ValueError("syntax error") |
| 103 | |
| 104 | if operation == "+": |
| 105 | result += operand |
| 106 | elif operation == "-": |
| 107 | result -= operand |
| 108 | elif operation == "*": |
| 109 | result *= operand |
| 110 | elif operation == "/": |
| 111 | # Edge Case: Division by zero |
| 112 | if operand == 0: |
| 113 | raise ValueError("syntax error") |
| 114 | result //= operand # Integer division as per examples |
| 115 | |
| 116 | return result |
| 117 | # Handled Edge Cases: Empty input, non-math questions, missing question mark, |
| 118 | # expressions starting/ending with operations, |
| 119 | # consecutive numbers/operations, division by zero, |
| 120 | # unknown operations, missing 'by' in multiplied/divided operations, |
| 121 | # even number of tokens, invalid syntax |