Regex for non-continuous bit 1 segments

Question

Given a series of bits, e.g 10100011110010101 and 010001001010100.

How can I write a regular expression to reflect the patterns where no 1s are neighbors?

For example, 010001001010100 is a good one, but 10100011110010101 is not as there are 1s neighboring.

edit:

Sorry my above statement may be misleading. i don't want to check whether a sequence is non-1-neighboring. I want to use an regex to find all non-1-neighborings.

Assume I have a very lone series of bits, I want to write a regex to find out all sub sequences where no 1s are neighbors.

How about simply detecting the undesired cases and filter them out? — Thomas, Jan 13 '14 at 15:14
Does that imply that the string shouldn't contain `11` _or_ (start & end with `1`)? — devnull, Jan 13 '14 at 15:15
Are we talking strings of zeros and ones, or actual bit vectors? E.g. 01000001 would be 0x41 or ASCII "A". — tripleee, Jan 13 '14 at 15:19
-1 for changing the question after receiving several good answers to the original question. — tripleee, Jan 13 '14 at 16:08

score 4 · Answer 1 · answered Jan 13 '14 at 15:15

4

Simply "11" will return true if neighboring ones exist.

Regards

answered Jan 13 '14 at 15:15

SamWhan

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Sorry my above statement may be misleading. i don't want to check whether a sequence is non-1-neighboring. I want to use an regex to find all non-1-neighborings. – Jackson Tale Jan 13 '14 at 15:22

score 3 · Answer 2 · answered Jan 13 '14 at 15:14

3

You can try with following regex:

^0*(10+)*1?$

answered Jan 13 '14 at 15:14

hsz

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@C.B. Ok, I've edited. I know that reverted regex will be simpler, but I give it as an example. :-) – hsz Jan 13 '14 at 15:16
To fix this for the updated requirements, if you change `^` to `(^1)?` and `1?$` to `(1?$)?` you get pretty much the same as mine. The grouping is different but the basic idea is identical. – tripleee Jan 13 '14 at 16:06

score 1 · Accepted Answer · answered Jan 13 '14 at 15:25

1

The following regex will match any run of zeros where any embedded ones are not adjacent to another one. A leading or trailing one at beginning/end of string is accepted as well.

(^1)?0+(10+)*(1$)?

A test with your example strings yields:

bash$ grep -Eo '(^1)?0+(10+)*(1$)?' <<<10100011110010101
101000
0010101

bash$ grep -Eo '(^1)?0+(10+)*(1$)?' <<<010001001010100
010001001010100

answered Jan 13 '14 at 15:25

tripleee

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They are very similar, but @hsz's answer was submitted before you changed your requirements, so it doesn't match the partial runs. – tripleee Jan 13 '14 at 16:01

score 0 · Answer 4 · answered Jan 13 '14 at 15:18

0

Search for 11+, i.e. a 1 followed by at least one 1.

answered Jan 13 '14 at 15:18

sp00m

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Assume I have a very lone series of bits, I want to write a regex to find out all sub sequences where no 1s are neighbors. – Jackson Tale Jan 13 '14 at 15:19
1

@JacksonTale For example in `10100011110010101`, what should match then? – sp00m Jan 13 '14 at 15:24

Casimir et Hippolyte · Answer 5 · 2014-01-13T16:05:24.850

0

You can use this, if your regex flavor supports lookarounds:

(?<!1)1(?!1)

(?<!1): not preceded by 1
(?!1): not followed by 1

If your regex flavor doesn't support lookarounds, you can use a capturing group and 2 non capturing groups instead of:

(?:^|0)(1)(?:0|$)

(Note that the capturing group is usefull only if you want to catch the offset of the capture with an appropriate function)

edited Jan 13 '14 at 16:05

answered Jan 13 '14 at 15:33

Casimir et Hippolyte

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It says true for `10100011110010101` – Toto Jan 13 '14 at 15:39
@M42: I know but the question has been edited. The OP "want to use an regex to find all non-1-neighborings" – Casimir et Hippolyte Jan 13 '14 at 16:07

Regex for non-continuous bit 1 segments

5 Answers5