剑指offer 表示数值的字符(面试题20. 表示数值的字符串)

2023-05-22 18:21 1阅读 0赞

**题目描述：**

请实现一个函数用来判断字符串是否表示数值（包括整数和小数）。例如，字符串 `"+100","5e2","-123","3.1416"和"-1E-16"` 都表示数值。 但是`"12e","1a3.14","1.2.3","+-5"和"12e+4.3"` 都不是。

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**解题思路1:**

使用float类型转换函数,出错就捕获错误,返回False

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**代码1：**

class Solution:
        # s字符串
        def isNumeric(self, s):
            try:
                ss = float(s)
                return True
            except:
                return False

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**解题思路2:**

正则表达式

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**代码2：**

'''
    使用re判断
    * 匹配前面出现的正则表达式零次或多次
    + 匹配前面出现的正则表达式1次或多次
    ? 匹配前面出现的正则表达式0次或1次
    正则中三部分:
    1. ^[\+\-]?[0-9]* 判断字符串头是否存在符号后面
    2. (\.[0-9]*)? 判断是否存在小数点
    3. ([eE][\+\-]?[0-9]+)? 这里[0-9]后面是+,因为出现e或者E后必须有数字.
    '''
    import re
    class Solution:
        def isNumber(self, s):
    		return re.match(r"^[\+\-]?[0-9]*(\.[0-9]*)?([eE][\+\-]?[0-9]+)?$", s)

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**参考链接:**

[God\_white][God_white]

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**题目来源：**

[https://www.nowcoder.com/practice/6f8c901d091949a5837e24bb82a731f2?tpId=13&tqId=11206&tPage=1&rp=1&ru=/ta/coding-interviews&qru=/ta/coding-interviews/question-ranking][https_www.nowcoder.com_practice_6f8c901d091949a5837e24bb82a731f2_tpId_13_tqId_11206_tPage_1_rp_1_ru_ta_coding-interviews_qru_ta_coding-interviews_question-ranking]

[https://leetcode-cn.com/problems/biao-shi-shu-zhi-de-zi-fu-chuan-lcof/][https_leetcode-cn.com_problems_biao-shi-shu-zhi-de-zi-fu-chuan-lcof]

[God_white]: https://blog.csdn.net/Sun_White_Boy/article/details/83659370?ops_request_misc=%257B%2522request%255Fid%2522%253A%2522158709415919726867812481%2522%252C%2522scm%2522%253A%252220140713.130102334.pc%255Fall.%2522%257D&request_id=158709415919726867812481&biz_id=0&utm_source=distribute.pc_search_result.none-task-blog-2~all~first_rank_v2~rank_v25-1
[https_www.nowcoder.com_practice_6f8c901d091949a5837e24bb82a731f2_tpId_13_tqId_11206_tPage_1_rp_1_ru_ta_coding-interviews_qru_ta_coding-interviews_question-ranking]: https://www.nowcoder.com/practice/6f8c901d091949a5837e24bb82a731f2?tpId=13&tqId=11206&tPage=1&rp=1&ru=/ta/coding-interviews&qru=/ta/coding-interviews/question-ranking
[https_leetcode-cn.com_problems_biao-shi-shu-zhi-de-zi-fu-chuan-lcof]: https://leetcode-cn.com/problems/biao-shi-shu-zhi-de-zi-fu-chuan-lcof/