Sha256: a6064ed0854e2622b27665c2309dd620002b959dddfa9cf2074fd2887b35e1eb
Contents?: true
Size: 1.61 KB
Versions: 25
Compression:
Stored size: 1.61 KB
Contents
module HashDiff
# @private
#
# caculate array difference using LCS algorithm
# http://en.wikipedia.org/wiki/Longest_common_subsequence_problem
def self.lcs(a, b, options = {})
opts = { :similarity => 0.8 }.merge!(options)
opts[:prefix] = prefix_append_array_index(opts[:prefix], '*', opts)
return [] if a.size == 0 or b.size == 0
a_start = b_start = 0
a_finish = a.size - 1
b_finish = b.size - 1
vector = []
lcs = []
(b_start..b_finish).each do |bi|
lcs[bi] = []
(a_start..a_finish).each do |ai|
if similar?(a[ai], b[bi], opts)
topleft = (ai > 0 and bi > 0)? lcs[bi-1][ai-1][1] : 0
lcs[bi][ai] = [:topleft, topleft + 1]
elsif
top = (bi > 0)? lcs[bi-1][ai][1] : 0
left = (ai > 0)? lcs[bi][ai-1][1] : 0
count = (top > left) ? top : left
direction = :both
if top > left
direction = :top
elsif top < left
direction = :left
else
if bi == 0
direction = :top
elsif ai == 0
direction = :left
else
direction = :both
end
end
lcs[bi][ai] = [direction, count]
end
end
end
x = a_finish
y = b_finish
while x >= 0 and y >= 0 and lcs[y][x][1] > 0
if lcs[y][x][0] == :both
x -= 1
elsif lcs[y][x][0] == :topleft
vector.insert(0, [x, y])
x -= 1
y -= 1
elsif lcs[y][x][0] == :top
y -= 1
elsif lcs[y][x][0] == :left
x -= 1
end
end
vector
end
end
Version data entries
25 entries across 22 versions & 5 rubygems