LeetCode:String to Integer (atoi)

這一題我總結主要考慮的異常case如下：

• 空字符串

• 都是空白符

• 空白符+正負號結束

• 空白符+異常字符

• 空白符+數字+異常字符

• 還有轉換過程中的數據溢出

代碼如下：

    #! /usr/bin/env python
    # -*- coding:gbk -*-

    class Solution(object):
        def myAtoi(self, str):
            """
            :type str: str
            :rtype: int
            """

            digital_dict = {'0':0, '1':1, '2':2, '3':3, '4':4, '5':5, '6':6, '7':7, '8':8, '9':9}
            if str == "":
                return 0
            while str.startswith(' '):
                str = str[1:]
            if str == "":
                return 0
            is_negtive = 0
            if str[0] == '-':
                is_negtive = 1
                str = str[1:]
            elif str[0] == '+':
                str = str[1:]
            if str == "":
                return 0
            while str.startswith('0'):
                str = str[1:]
            if str == "":
                return 0
            ret = 0
            for i in range(len(str)):
                if not digital_dict.has_key(str[i]):
                    break
                ret = ret*10 + digital_dict[str[i]]
                if not is_negtive and ret >= (1<<31):
                    return (1<<31) - 1
                elif is_negtive and ret > (1<<31):
                    return -(1<<31)
            if not is_negtive:
                return ret
            else:
                return -ret

    if __name__ == "__main__":
        s = Solution()
        print s.myAtoi('12345')
        print s.myAtoi('-12345')
        print s.myAtoi('   -12345')
        print s.myAtoi('   -')
        print s.myAtoi('   +')
        #print s.myAtoi('   12345')
        #print s.myAtoi('   1234 5')
        print s.myAtoi('   1234a5')
        #print s.myAtoi('1234599999999999999')
        #print s.myAtoi('-1234599999999999999')