String to Integer (atoi)
Implement myAtoi(s) which converts a string to a 32-bit signed integer:
- Skip leading whitespace
- Read an optional '+' or '-' sign
- Read digits until a non-digit character or end of string
- Clamp the result to the 32-bit signed integer range: [-2^31, 2^31 - 1]
- Return 0 if no digits were read
Example:
-42
-42
- The function skips leading whitespace, but since there's none in the input
-42, it proceeds to the next step. - It reads the optional sign, which is
-in this case, indicating a negative number. - The function then reads the digits
42and converts them to an integer: result=−1⋅42=−42. - Since −42 is within the 32-bit signed integer range [−231,231−1], the result is not clamped and is returned as is.
- The final output is
-42.
Constraints:
- 0 <= len(s) <= 200
- s consists of English letters, digits, ' ', '+', '-', '.'
Background Knowledge
The problem "String to Integer (atoi)" involves converting a string to a 32-bit signed integer. To tackle this problem, it's essential to understand the basics of string manipulation and integer overflow. In programming, strings are sequences of characters, and manipulating them often involves iterating over these characters to extract or transform information. Integer overflow occurs when a value exceeds the maximum limit of its data type, which in this case is a 32-bit signed integer. The 32-bit signed integer range is [−231,231−1], meaning any value outside this range will need to be clamped to fit within it.
Understanding the concept of state machines can also be beneficial. A state machine is a mathematical model that can be in one of a finite number of states and can change state based on certain rules. In the context of this problem, you might consider states such as "initial," "sign encountered," and "digit encountered" to guide your parsing of the input string. This approach helps in systematically handling different parts of the input string.
The problem also touches on error handling, as it specifies what to do in cases where no digits are found (return 0) or when the result exceeds the 32-bit signed integer range (clamp the result). Being able to gracefully handle unexpected or edge-case inputs is a crucial aspect of robust programming.
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