Regex to match consecutive n (alpha numeric)

问题

I am trying to match consecutive n(alpha numeric) characters in a string.

Where n = 3

i7g172w2n             YES (it has 3 consecutive number)

adab172cd             NO (it has 4 consecutive alpha even though it has 3 consecutive number)

aaa172afa             YES (it has 3 consecutive number and 3 consecutive alpha)

ab21cd172             YES

abc21a3d3             YES

Can some one help me.

Here is my regex : (\D(\d{3})\D)|\d([a-z]{3})\d not working.

回答1:

Try with following regex.

Regex: ^(?:(?:\d{0,3}[a-z]{1,3}\d{1,3})+|(?:[a-z]{0,3}\d{1,3}[a-z]{1,3})+)$

Explanation: Basically what I have done is matched following patterns.

(?:\d{0,3}[a-z]{1,3}\d{1,3})+
- ( 0-3 Digit 1-3 Alphabets 1-3 Digits ) <- More than one time.
(?:[a-z]{0,3}\d{1,3}[a-z]{1,3})+
- ( 0-3 Alphabets 1-3 Digits 1-3 Alphabets ) <- More than one time.

Since both are in alternation, hence either of these pattern will be matched.

For string i7g172w2n sub matches will be i-7-g-172-w-2-n. Which fits into the specifications.

For string adsb172cd sub matches will be adsb-172-cd. Since adsb exceeds length 3. Hence won't be matched.

Similarly for abc2p7373, 7373 exceeds length 3.

Regex101 Demo

回答2:

While there almost certainly is a pure-regex solution to this problem, it's going to be an incomprehensible mess involving lookahead assertions. If you do some of the work in code instead of regex, the problem becomes much more straightforward (Python shown):

import re

def consecutive(s, n):
    matches = re.findall("\d+|[a-z]+", s)
    longest = max(map(len, matches))
    return longest == n

for test in ["i7g172w2n", "adab172cd", "aaa172afa", "ab21cd172", "abc21a3d3", "12a3b3b3b"]:
    print test, consecutive(test, 3)

Basically, it verifies that the longest consecutive sequence of digits or letters is exactly the required number, no more nor less. Output:

i7g172w2n True
adab172cd False
aaa172afa True
ab21cd172 True
abc21a3d3 True
12a3b3b3b False

来源：https://stackoverflow.com/questions/44170109/regex-to-match-consecutive-n-alpha-numeric

标签

regex

regex-negation