String to Integer (atoi)

Implement the myAtoi(string s) function, which converts a string to a 32-bit signed integer.

The algorithm for myAtoi(string s) is as follows:

1. Whitespace: Ignore any leading whitespace (" ").
2. Signedness: Determine the sign by checking if the next character is '-' or '+', assuming positivity if neither present.
3. Conversion: Read the integer by skipping leading zeros and stopping at the first non-digit character or at the end of the string.
4. Rounding: If the integer is out of the 32-bit signed integer range [-2^31, 2^31 - 1], clamp the integer to remain in the range.

Return the integer as the final result.

Example 1:

Input: s = "42"
Output: 42
Explanation: 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)

Example 2:

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

Example 3:

Input: s = "1337c0d3"
Output: 1337
Explanation: Conversion stops at 'c' which is not a digit.

Example 4:

Input: s = "0-1"
Output: 0
Explanation: '0' is read, then '-' stops conversion.

Example 5:

Input: s = "words and 987"
Output: 0
Explanation: The first non-whitespace character is 'w', which is not a digit or '+'/'-'. Conversion cannot be performed.