text: #
  # [8] String to Integer (atoi)
  #
  # https://leetcode.com/problems/string-to-integer-atoi/description/
  #
  # algorithms
  # Medium (14.12%)
  # Total Accepted:    259.4K
  # Total Submissions: 1.8M
  # Testcase Example:  '"42"'
  #
  # 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.
  # 
  # 
  # 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.
  # 
  #
  class Solution:
      def myAtoi(self, str: str) -> int:
          int_max = 2 ** 31 - 1
          int_min = -2 ** 31
  
          sign = 1
          res = 0
          i = 0
  
          while i < len(str):
  
              if str[i] == ' ':
                  i += 1
                  continue
  
              if str[i] == '+' or str[i] == '-':
                  sign = -1 if str[i] == '-' else 1
                  i += 1
  
              while i < len(str) and str[i].isdigit():
                  digit = int(str[i])  * sign
                  res = res * 10 + digit
  
                  if res >= int_max:
                      return int_max
                  if res <= int_min:
                      return int_min
                  i += 1
              
              break
  
          return res