| 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 unknown operations, or is not a math question |
| 13 | """ |
| 14 | # Edge Case: Non-math questions |
| 15 | if not question.startswith("What is"): |
| 16 | raise ValueError("syntax error") |
| 17 | |
| 18 | # Remove the "What is " prefix and the trailing question mark |
| 19 | expression = question[8:-1].strip() |
| 20 | |
| 21 | # Edge Case: Empty expression after "What is" |
| 22 | if not expression: |
| 23 | raise ValueError("syntax error") |
| 24 | |
| 25 | # Tokenize the expression |
| 26 | tokens = [] |
| 27 | i = 0 |
| 28 | while i < len(expression): |
| 29 | if expression[i].isspace(): |
| 30 | i += 1 |
| 31 | continue |
| 32 | elif expression[i].isdigit() or (expression[i] == '-' and i < len(expression) - 1 and expression[i+1].isdigit()): |
| 33 | # Parse negative numbers |
| 34 | start = i |
| 35 | if expression[i] == '-': |
| 36 | i += 1 |
| 37 | while i < len(expression) and (expression[i].isdigit() or expression[i] == '.'): |
| 38 | i += 1 |
| 39 | # Edge Case: Numbers with decimal points |
| 40 | num_str = expression[start:i] |
| 41 | if '.' in num_str: |
| 42 | try: |
| 43 | num_val = float(num_str) |
| 44 | # Edge Case: Non-integer floats |
| 45 | if not num_val.is_integer(): |
| 46 | raise ValueError("syntax error") |
| 47 | tokens.append(int(num_val)) |
| 48 | except ValueError: |
| 49 | raise ValueError("syntax error") |
| 50 | else: |
| 51 | tokens.append(int(num_str)) |
| 52 | else: |
| 53 | # Parse operators and words |
| 54 | start = i |
| 55 | while i < len(expression) and not expression[i].isspace(): |
| 56 | i += 1 |
| 57 | word = expression[start:i] |
| 58 | if word == "plus": |
| 59 | tokens.append("+") |
| 60 | elif word == "minus": |
| 61 | tokens.append("-") |
| 62 | elif word == "multiplied": |
| 63 | # Check for "by" after "multiplied" |
| 64 | if i < len(expression): |
| 65 | # Skip spaces |
| 66 | while i < len(expression) and expression[i].isspace(): |
| 67 | i += 1 |
| 68 | # Check for "by" |
| 69 | if i + 1 < len(expression) and expression[i:i+2] == "by": |
| 70 | # Skip "by" |
| 71 | i += 2 |
| 72 | tokens.append("*") |
| 73 | else: |
| 74 | # Edge Case: "multiplied" without "by" |
| 75 | raise ValueError("syntax error") |
| 76 | else: |
| 77 | # Edge Case: "multiplied" at end of expression |
| 78 | raise ValueError("syntax error") |
| 79 | elif word == "divided": |
| 80 | # Check for "by" after "divided" |
| 81 | if i < len(expression): |
| 82 | # Skip spaces |
| 83 | while i < len(expression) and expression[i].isspace(): |
| 84 | i += 1 |
| 85 | # Check for "by" |
| 86 | if i + 1 < len(expression) and expression[i:i+2] == "by": |
| 87 | # Skip "by" |
| 88 | i += 2 |
| 89 | tokens.append("/") |
| 90 | else: |
| 91 | # Edge Case: "divided" without "by" |
| 92 | raise ValueError("syntax error") |
| 93 | else: |
| 94 | # Edge Case: "divided" at end of expression |
| 95 | raise ValueError("syntax error") |
| 96 | else: |
| 97 | # Edge Case: Unknown operations - check if this creates syntax error |
| 98 | # If we have a valid number-operator pattern but unknown word, it's syntax error |
| 99 | if tokens and isinstance(tokens[-1], str) and tokens[-1] in ["+", "-", "*", "/"]: |
| 100 | raise ValueError("syntax error") |
| 101 | else: |
| 102 | raise ValueError("unknown operation") |
| 103 | |
| 104 | # Edge Case: Empty tokens list |
| 105 | if not tokens: |
| 106 | raise ValueError("syntax error") |
| 107 | |
| 108 | # Edge Case: Expression starting with an operator |
| 109 | if isinstance(tokens[0], str): |
| 110 | raise ValueError("syntax error") |
| 111 | |
| 112 | # Evaluate the expression from left to right |
| 113 | # Edge Case: Single number |
| 114 | if len(tokens) == 1: |
| 115 | return tokens[0] |
| 116 | |
| 117 | # Edge Case: Even number of tokens (should be odd: number, operator, number, ...) |
| 118 | if len(tokens) % 2 == 0: |
| 119 | raise ValueError("syntax error") |
| 120 | |
| 121 | result = tokens[0] |
| 122 | i = 1 |
| 123 | while i < len(tokens): |
| 124 | # Edge Case: Missing operator or number in sequence |
| 125 | if i + 1 >= len(tokens): |
| 126 | raise ValueError("syntax error") |
| 127 | |
| 128 | operator = tokens[i] |
| 129 | operand = tokens[i + 1] |
| 130 | |
| 131 | # Edge Case: Non-operator where operator expected |
| 132 | if not isinstance(operator, str): |
| 133 | raise ValueError("syntax error") |
| 134 | |
| 135 | # Edge Case: Non-number where number expected |
| 136 | if not isinstance(operand, int): |
| 137 | raise ValueError("syntax error") |
| 138 | |
| 139 | if operator == "+": |
| 140 | result += operand |
| 141 | elif operator == "-": |
| 142 | result -= operand |
| 143 | elif operator == "*": |
| 144 | result *= operand |
| 145 | elif operator == "/": |
| 146 | # Edge Case: Division by zero |
| 147 | if operand == 0: |
| 148 | raise ValueError("syntax error") # Following test expectations |
| 149 | result //= operand # Integer division as per examples |
| 150 | else: |
| 151 | # Edge Case: Unknown operator in tokens |
| 152 | raise ValueError("unknown operation") |
| 153 | |
| 154 | i += 2 |
| 155 | |
| 156 | return result |
| 157 | # Handled Edge Cases: Non-math questions, empty expression, numbers with decimal points, non-integer floats, |
| 158 | # "multiplied" without "by", "divided" without "by", unknown operations, empty tokens list, |
| 159 | # expression starting with operator, single number, even number of tokens, missing operator/number in sequence, |
| 160 | # non-operator where operator expected, non-number where number expected, division by zero, unknown operator in tokens |