Re: common prefix?
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- Subject: Re: common prefix?
- From: Philippe Lhoste <PhiLho@...>
- Date: 2009年7月17日 10:51:39 +0200
On 16/07/2009 21:03, Petite Abeille wrote:
Does anyone has a little function to compute the common prefix of a list
of strings?
Perhaps not the best method, but it is an amusing approach, I think:
function CommonPrefix(list)
if #list == 0 then return '' end
local first = list[1]
local SEP = '1円'
local listLen = #list
local cl = SEP .. table.concat(list, SEP)
local prefix = ''
local pLen, maxLen = 0, #first
local bOK = false
repeat
pLen = pLen + 1
prefix = string.sub(first, 1, pLen)
--~ print(pLen .. ' ' .. prefix)
local pattern = string.rep(SEP .. prefix .. '.-', listLen)
--~ print(pattern)
bOK = pLen <= maxLen and string.match(cl, pattern)
until not bOK
return string.sub(first, 1, pLen - 1)
end
print(CommonPrefix({ 'foobarbaz', 'foobar', 'foo' }))
print(CommonPrefix({ 'foo', 'foobarbaz', 'foobar', 'foorass' }))
print(CommonPrefix({ 'one' }))
print(CommonPrefix({ 'x', 'y' }))
print(CommonPrefix({ }))
I would have preferred to write:
local pattern = SEP .. prefix .. '.-{' .. listLen .. '}'
(perhaps faster) but it is not possible in standard Lua.
--
Philippe Lhoste
-- (near) Paris -- France
-- http://Phi.Lho.free.fr
-- -- -- -- -- -- -- -- -- -- -- -- -- --