leetcode: 8. String to Integer (atoi)

Problem

# Implement atoi to convert a string to an integer.## Hint: Carefully consider all possible input cases.# If you want a challenge, please do not see below and ask yourself what are the possible input cases.## Notes: # It is intended for this problem to be specified vaguely (ie, no given input specs).# You are responsible to gather all the input requirements up front.## Update (2015-02-10):# The signature of the C++ function had been updated.# If you still see your function signature accepts a const char * argument, please click the reload button to reset your code definition.## spoilers alert... click to show requirements for atoi.## Requirements for atoi:## 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.# If the correct value is out of the range of representable values, INT_MAX (2147483647) or INT_MIN (-2147483648) is returned.

AC

class Solution():    def myAtoi(self, str):        INT_MAX =  2147483647        INT_MIN = -2147483648        i, sign, result = 0, 1, 0        if not str:            return result        while i < len(str) and str[i].isspace():            i += 1        if str[i] == "+":            i += 1        elif str[i] == "-":            sign = -1            i += 1        while i < len(str) and "0" <= str[i] <= "9":            if result > (INT_MAX - int(str[i])) // 10:                return INT_MAX if sign > 0 else INT_MIN            result = result * 10 + int(str[i])            i += 1        return result * signif __name__ == '__main__':    assert Solution().myAtoi("+-2") == 0    assert Solution().myAtoi("") == 0    assert Solution().myAtoi("-1") == -1    assert Solution().myAtoi("2147483647") == 2147483647    assert Solution().myAtoi("2147483648") == 2147483647    assert Solution().myAtoi("-2147483648") == -2147483648    assert Solution().myAtoi("-2147483649") == -2147483648