String to Integer (atoi) Python Solution

lcpy gen -n 8   # by problem number
lcpy gen -s string_to_integer_atoi   # by problem name

Input: s = "42"
Output: 42

The underlined characters are what is read in and the caret is the current reader position.
Step 1: "42" (no characters read because there is no leading whitespace)
         ^
Step 2: "42" (no characters read because there is neither a '-' nor '+')
         ^
Step 3: "42" ("42" is read in)
           ^

Input: s = "   -042"
Output: -42

Step 1: "   -042" (leading whitespace is read and ignored)
            ^
Step 2: "   -042" ('-' is read, so the result should be negative)
             ^
Step 3: "   -042" ("042" is read in, leading zeros ignored in the result)
               ^

Input: s = "1337c0d3"
Output: 1337

Step 1: "1337c0d3" (no characters read because there is no leading whitespace)
         ^
Step 2: "1337c0d3" (no characters read because there is neither a '-' nor '+')
         ^
Step 3: "1337c0d3" ("1337" is read in; reading stops because the next character is a non-digit)
             ^

Input: s = "0-1"
Output: 0

Step 1: "0-1" (no characters read because there is no leading whitespace)
         ^
Step 2: "0-1" (no characters read because there is neither a '-' nor '+')
         ^
Step 3: "0-1" ("0" is read in; reading stops because the next character is a non-digit)
          ^

Input: s = "words and 987"
Output: 0

class Solution:
    # Time: O(n)
    # Space: O(1)
    def my_atoi(self, s: str) -> int:
        i = 0
        n = len(s)

        # Skip whitespace
        while i < n and s[i] == " ":
            i += 1

        if i == n:
            return 0

        # Check sign
        sign = 1
        if s[i] in {"+", "-"}:
            sign = -1 if s[i] == "-" else 1
            i += 1

        # Convert digits
        result = 0
        while i < n and s[i].isdigit():
            result = result * 10 + int(s[i])
            i += 1

        result *= sign

        # Clamp to 32-bit range
        return max(-(2**31), min(2**31 - 1, result))