8. String to Integer (atoi)

https://leetcode.com/problems/string-to-integer-atoi

Python

Test cases are really special

• "42"
• "-41"
• "00000-42a1234"
• " +0 123"
• "words and 987"
• "-"
• "-5-"
• "-+12"

class Solution:
    def myAtoi(self, s: str) -> int:
        chars = s.strip()
        num_chars = []

        if not chars:
            return 0

        seem_num = False
        seem_sign = False

        for i in range(len(chars)):
            char = chars[i]

            if not char.isnumeric():
                if seem_num:
                    break
                elif char == '+':
                    if seem_sign:
                        return 0
                    seem_sign = True
                elif char == '-':
                    if seem_sign:
                        return 0
                    seem_sign = True
                    num_chars.append('-')
                else:
                    break
            else:
                num_chars.append(char)
                seem_num = True

        if not num_chars or (len(num_chars) == 1 and num_chars[0] == '-'):
            return 0

        number = int(''.join(num_chars))
        limit = 2**31

        if number > limit-1:
            return limit-1
        if number < -limit:
            return -limit
        return number