'''
LeetCode | Problem 8: String to Integer (atoi)

Task:
    Implement atoi which converts a string to an integer.

    The function first discards as many whitespace characters as necessary
    until the first non-whitespace character is found. Then, starting from this
    character, takes an optional initial plus or minus sign followed by as many
    numerical digits as possible, and interprets them as a numerical value.

    The string can contain additional characters after those that form the
    integral number, which are ignored and have no effect on the behavior of
    this function.

    If the first sequence of non-whitespace characters in str is not a valid
    integral number, or if no such sequence exists because either str is empty
    or it contains only whitespace characters, no conversion is performed.

    If no valid conversion could be performed, a zero value is returned.

Note:
    - Only the space character ' ' is considered as whitespace character.
    - Assume we are dealing with an environment which could only store integers
        within the 32-bit signed integer range: [−231,  231 − 1]. If the
        numerical value is out of the range of representable values, INT_MAX
        (231 − 1) or INT_MIN (−231) is returned.

Examples:
    Example 1:
        Input: "42"
        Output: 42

    Example 2:
        Input: "   -42"
        Output: -42
        Explanation: The first non-whitespace character is '-', which is the
            minus sign.Then take as many numerical digits as possible,
            which gets 42.

    Example 3:
        Input: "4193 with words"
        Output: 4193
        Explanation: Conversion stops at digit '3' as the next character is not
            a numerical digit.

    Example 4:
        Input: "words and 987"
        Output: 0
        Explanation: The first non-whitespace character is 'w', which is not a
            numerical digit or a +/- sign. Therefore no valid conversion could
            be performed.

    Example 5:
        Input: "-91283472332"
        Output: -2147483648
        Explanation: The number "-91283472332" is out of the range of a
            32-bit signed integer.Thefore INT_MIN (−231) is returned.
'''
INT_MAX, INT_MIN = 2**31-1, -2**31

class Solution:
    def myAtoi(self, str: str) -> int:
        str = str.strip()
        if not str:
            return 0

        if str[0].isdigit() or str[0] in '+-':
            result = str[0]
            for c in str[1:]:
                if not c.isdigit():
                    break
                result += c

            if len(result) == 1 and not result.isdigit():
                return 0

            return max(min(int(result), INT_MAX), INT_MIN)
        else:
            return 0
