Extract every substring from string on regex match?

Question

I want to extract all 0s between two 1s and group them from a binary number. So far I've done this,

529.to_s(2).scan(/1(0+)1/)

the output is array with one element only, although i want two elements. That is

529 => binary => 1000010001

["0000","000"]

From the answer you have accepted, it seems you only wanted zeros from a binary number, whether they are surrounded by ones doesn't seem to matter. If you only wanted zeros, why didn't you try 529.to_s(2).scan /0+/ matches one or more zeros regardless of the presence of ones. In any case, a binary number contains only zeros and ones. So the only other thing zeros could be surrounded is ones. — bsd
– bsd, Commented Sep 8, 2013 at 12:42

sawa · Accepted Answer · 2013-09-08 11:57:06Z

2

529.to_s(2).scan(/(?<=1)0+(?=1)/)
# => ["0000", "000"]

answered Sep 8, 2013 at 11:57

sawa

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Arup Rakshit · Accepted Answer · 2013-09-08 12:20:05Z

0

How is this ?

a = 529.to_s(2).split("1")
a.delete("")
a # => ["0000", "000"]

edited Sep 8, 2013 at 12:20

answered Sep 8, 2013 at 11:55

Arup Rakshit

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6 Comments

bsd Over a year ago

You could write that as 529.to_s(2).scan /0+/. Not sure whether OP really wanted that.

Arup Rakshit Over a year ago

@bsd He wants - I want to extract all 0s between two 1s :)

bsd Over a year ago

Try it out with numbers like 8, 4, 2, 14. See if the zeros are really surrounded by ones.

Arup Rakshit Over a year ago

@bsd a = 8.to_s(2).split("1") # => ["", "000"] I got.

bsd Over a year ago

But where is the second one in 1000. There is only one one.

|

bsd · Accepted Answer · 2013-09-08 12:33:30Z

0

all 0s between two 1s and group

So I presume you don't want matches like 10, 100, 111000, 1000 and so on. The easiest way is to find the left and right index of the first one from the start and end and then start looking only for zeros.

Here is one way.

bin=8.to_s(2) #=> 1000
bin[bin.index('1')..bin.rindex('1')].scan /0+/
#=> []

bin=529.to_s(2) #=> 1000
bin[bin.index('1')..bin.rindex('1')].scan /0+/
#=> ["0000", "000"]

Beware of 0. It does not contains any one and you get nil.

edited Sep 8, 2013 at 12:33

answered Sep 8, 2013 at 12:24

bsd

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