| 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 evaluating the math expression |
| 10 | |
| 11 | Raises: |
| 12 | ValueError: If the question is malformed, contains unsupported operations, |
| 13 | or is not a valid math question |
| 14 | """ |
| 15 | # Edge Case: Empty or None input |
| 16 | if not question: |
| 17 | raise ValueError("syntax error") |
| 18 | |
| 19 | # Edge Case: Non-math questions |
| 20 | if not question.startswith("What is"): |
| 21 | raise ValueError("unknown operation") |
| 22 | |
| 23 | # Edge Case: Malformed questions without a question mark |
| 24 | if not question.endswith("?"): |
| 25 | raise ValueError("syntax error") |
| 26 | |
| 27 | # Remove "What is" and "?" to get the expression |
| 28 | expression = question[8:-1].strip() |
| 29 | |
| 30 | # Edge Case: Empty expression after removing "What is" and "?" |
| 31 | if not expression: |
| 32 | raise ValueError("syntax error") |
| 33 | |
| 34 | # Tokenize the expression |
| 35 | tokens = [] |
| 36 | i = 0 |
| 37 | while i < len(expression): |
| 38 | if expression[i].isspace(): |
| 39 | i += 1 |
| 40 | continue |
| 41 | |
| 42 | # Handle negative numbers |
| 43 | if expression[i] == '-' and (i == 0 or expression[i-1] in ' '): |
| 44 | i += 1 |
| 45 | if i >= len(expression) or not expression[i].isdigit(): |
| 46 | # This is a minus operator, not a negative number |
| 47 | tokens.append('-') |
| 48 | continue |
| 49 | |
| 50 | num_start = i - 1 |
| 51 | while i < len(expression) and (expression[i].isdigit() or expression[i] == '.'): |
| 52 | i += 1 |
| 53 | tokens.append(int(expression[num_start:i])) |
| 54 | continue |
| 55 | |
| 56 | # Handle positive numbers |
| 57 | if expression[i].isdigit() or (expression[i] == '-' and i < len(expression) - 1 and expression[i+1].isdigit()): |
| 58 | num_start = i |
| 59 | if expression[i] == '-': |
| 60 | i += 1 |
| 61 | while i < len(expression) and (expression[i].isdigit() or expression[i] == '.'): |
| 62 | i += 1 |
| 63 | tokens.append(int(expression[num_start:i])) |
| 64 | continue |
| 65 | |
| 66 | # Handle operators |
| 67 | if expression[i:].startswith("plus"): |
| 68 | tokens.append("+") |
| 69 | i += 4 |
| 70 | elif expression[i:].startswith("minus"): |
| 71 | tokens.append("-") |
| 72 | i += 5 |
| 73 | elif expression[i:].startswith("multiplied by"): |
| 74 | tokens.append("*") |
| 75 | i += 13 |
| 76 | elif expression[i:].startswith("divided by"): |
| 77 | tokens.append("/") |
| 78 | i += 10 |
| 79 | else: |
| 80 | # Edge Case: Unsupported operations |
| 81 | raise ValueError("unknown operation") |
| 82 | |
| 83 | # Edge Case: Expression with no tokens |
| 84 | if not tokens: |
| 85 | raise ValueError("syntax error") |
| 86 | |
| 87 | # Edge Case: Expression starting with an operator (except negative number) |
| 88 | if tokens[0] in ['+', '*', '/']: |
| 89 | raise ValueError("syntax error") |
| 90 | |
| 91 | # Edge Case: Expression ending with an operator |
| 92 | if tokens[-1] in ['+', '-', '*', '/']: |
| 93 | raise ValueError("syntax error") |
| 94 | |
| 95 | # Evaluate the expression from left to right |
| 96 | result = tokens[0] |
| 97 | |
| 98 | # Edge Case: Single number |
| 99 | if len(tokens) == 1: |
| 100 | if not isinstance(result, int): |
| 101 | raise ValueError("syntax error") |
| 102 | return result |
| 103 | |
| 104 | i = 1 |
| 105 | while i < len(tokens): |
| 106 | # Edge Case: Consecutive operators |
| 107 | if tokens[i] in ['+', '-', '*', '/'] and (i + 1 >= len(tokens) or tokens[i + 1] in ['+', '-', '*', '/']): |
| 108 | raise ValueError("syntax error") |
| 109 | |
| 110 | # Edge Case: Consecutive numbers |
| 111 | if isinstance(tokens[i], int) and (i + 1 < len(tokens) and isinstance(tokens[i + 1], int)): |
| 112 | raise ValueError("syntax error") |
| 113 | |
| 114 | operator = tokens[i] |
| 115 | # Edge Case: Missing operand |
| 116 | if i + 1 >= len(tokens): |
| 117 | raise ValueError("syntax error") |
| 118 | |
| 119 | operand = tokens[i + 1] |
| 120 | # Edge Case: Invalid operand type |
| 121 | if not isinstance(operand, int): |
| 122 | raise ValueError("syntax error") |
| 123 | |
| 124 | if operator == "+": |
| 125 | result += operand |
| 126 | elif operator == "-": |
| 127 | result -= operand |
| 128 | elif operator == "*": |
| 129 | result *= operand |
| 130 | elif operator == "/": |
| 131 | # Edge Case: Division by zero |
| 132 | if operand == 0: |
| 133 | raise ValueError("syntax error") # Or we could raise ZeroDivisionError |
| 134 | result //= operand # Integer division as per examples |
| 135 | else: |
| 136 | # Edge Case: Unknown operator (should not happen with our parsing) |
| 137 | raise ValueError("unknown operation") |
| 138 | |
| 139 | i += 2 |
| 140 | |
| 141 | return result |
| 142 | # Handled Edge Cases: Empty input, None input, non-math questions, questions without question mark, |
| 143 | # empty expressions, unsupported operations, expression starting with operator, |
| 144 | # expression ending with operator, single number, consecutive operators, |
| 145 | # consecutive numbers, missing operands, invalid operand types, division by zero |