Re: common prefix?

[Bulat Ziganshin <bulat.ziganshin@...>]

Hello Petite,

Thursday, July 16, 2009, 11:03:17 PM, you wrote:

> Does anyone has a little function to compute the common prefix of a
> list of strings?

str = aList[1] || ''
n = length (str)

for _,s in ipairs(aList) do
  while s:sub(1,n)~=str && n>0 do
    n=n-1
    str=s:sub(1,n)
  end
end



> E.g.:

> local aList = { 'foobarbaz', 'foobar', 'foo' }

> print( CommonPrefix( aList ) )

 >> foo

> TIA.

> Cheers,

> PA.

> P.S.

> FWIW, this is what I have concocted so far, but it looks, hmmm, not  
> right :)

> function LCP()
>      local aPrefix = nil

>      return function( aValue )
>          local aValue = tostring( aValue ) or ''
>                aPrefix = aPrefix or aValue
>          local aLength = math.min( aPrefix:len(), aValue:len() )

>          for anIndex = 0, aLength do
>              aPrefix = aPrefix:sub( 1, aLength - anIndex )

>              if aValue:find( aPrefix, 1, true ) then
>                  break
>              end
>          end

>          return aPrefix
>      end
> end


> local aList = { 'foobarbaz', 'foobar', 'foo' }
> local aLCP = LCP()

> for anIndex, aValue in ipairs( aList ) do
>      print( anIndex, aLCP( aValue ) )
> end


-- 
Best regards,
 Bulat                            mailto:Bulat.Ziganshin@gmail.com