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# frozen_string_literal: true
module Hashdiff
# @private
#
# caculate array difference using LCS algorithm
# http://en.wikipedia.org/wiki/Longest_common_subsequence_problem
def self.lcs(arraya, arrayb, options = {})
return [] if arraya.empty? || arrayb.empty?
opts = { similarity: 0.8 }.merge!(options)
opts[:prefix] = prefix_append_array_index(opts[:prefix], '*', opts)
a_start = b_start = 0
a_finish = arraya.size - 1
b_finish = arrayb.size - 1
vector = []
lcs = []
(b_start..b_finish).each do |bi|
lcs[bi] = []
(a_start..a_finish).each do |ai|
if similar?(arraya[ai], arrayb[bi], opts)
topleft = (ai > 0) && (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 = if top > left
:top
elsif top < left
:left
elsif bi.zero?
:top
elsif ai.zero?
:left
else
:both
end
lcs[bi][ai] = [direction, count]
end
end
end
x = a_finish
y = b_finish
while (x >= 0) && (y >= 0) && (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
89 entries across 87 versions & 8 rubygems