【leetcode】字符串转整数（String to Integer (atoi)）【python】

水深无声 2022-05-13 01:20 152阅读 0赞

[题目链接][Link 1]  
![这里写图片描述][70]

def isnum(x):
        if ord(x) >= ord('0') and ord(x) <= ord('9'):
            return 1
        else:
            return 0
    class Solution:
        def myAtoi(self, str):
            """ :type str: str :rtype: int """
    
            if str == '':
                return 0
            legal = 0
            string = ''
            for i in range(len(str)):
                if str[i] != ' ':
                    if str[i] == '+' or str[i] == '-' or isnum(str[i]):
                        #合法的
                        if str[i] == '+' or str[i] == '-':#只有加号减号
                            if i + 1 == len(str):
                                return 0
                            elif i + 1 < len(str):
                                if not isnum(str[i + 1]):
                                    return 0
                        legal = 1
                        string += str[i]
                        for j in range(i + 1, len(str)):
                            if isnum(str[j]):
                                string += str[j]
                            else:
                                break
                    else:#字符开头
                        return 0
                if legal == 1:#有一个数字了
                    break
            if legal == 0:
                return 0
            else:
                x = int(string)
                if x < -2 ** 31:
                    return -2 ** 31
                elif x > 2 ** 31 - 1:
                    return 2 ** 31 - 1
                else:
                    return x
    str = '3.14159'
    sol = Solution()
    print(sol.myAtoi(str))

[Link 1]: https://leetcode-cn.com/problems/string-to-integer-atoi/description/
[70]: /images/20220513/7b0f1fa2dfd7419c953a48ed38ea180d.png