flowingfog

偶尔刷题

  博客园  :: 首页  :: 新随笔  :: 联系 ::  :: 管理
  50 随笔 :: 0 文章 :: 0 评论

分析

难度 易

来源

https://leetcode.com/problems/valid-phone-numbers/

题目

Given a text file file.txt that contains list of phone numbers (one per line), write a one liner bash script to print all valid phone numbers.

You may assume that a valid phone number must appear in one of the following two formats: (xxx) xxx-xxxx or xxx-xxx-xxxx. (x means a digit)

You may also assume each line in the text file must not contain leading or trailing white spaces.

Example:

Assume that file.txt has the following content:

987-123-4567
123 456 7890
(123) 456-7890

Your script should output the following valid phone numbers:

987-123-4567
(123) 456-7890
解答

https://leetcode.com/problems/valid-phone-numbers/discuss/55478/Grep-e-solution-with-detailed-explanation-good-for-those-new-to-regex

1 grep -e '\(^[0-9]\{3\}-[0-9]\{3\}-[0-9]\{4\}$\)' -e '\(^([0-9]\{3\})[ ]\{1\}[0-9]\{3\}-\([0-9]\{4\}\)$\)'  file.txt
  1. In Bash, we use \ to escape next one trailing character;
  2. ^ is used to denote the beginning of a line
  3. $ is used to denote the end of a line
  4. {M} is used to denote to match exactly M times of the previous occurence/regex
  5. (...) is used to group pattern/regex together

Back to this problem: it requires us to match two patterns, for better readability, I used -e and separate the two patterns into two regexes, the first one matches this case: xxx-xxx-xxxx and the second one matches this case: (xxx) xxx-xxxx

加上-P(使用Perl的正则引擎)即可过滤出目标数据
1 grep -P '^(\d{3}-|\(\d{3}\) )\d{3}-\d{4}$' file.txt
注意上方的空格 
1 grep '^(\d{3}-|\(\d{3}\)[ ]{1})\d{3}-\d{4}$'  file.txt
这里使用[ ]{1}表示一个空格
posted on 2018-11-26 20:30  flowingfog  阅读(180)  评论(0编辑  收藏