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Diffstat (limited to 'ruby_1_8_6/lib/tsort.rb')
| -rw-r--r-- | ruby_1_8_6/lib/tsort.rb | 290 |
1 files changed, 0 insertions, 290 deletions
diff --git a/ruby_1_8_6/lib/tsort.rb b/ruby_1_8_6/lib/tsort.rb deleted file mode 100644 index a014e7f6c2..0000000000 --- a/ruby_1_8_6/lib/tsort.rb +++ /dev/null @@ -1,290 +0,0 @@ -#!/usr/bin/env ruby -#-- -# tsort.rb - provides a module for topological sorting and strongly connected components. -#++ -# - -# -# TSort implements topological sorting using Tarjan's algorithm for -# strongly connected components. -# -# TSort is designed to be able to be used with any object which can be -# interpreted as a directed graph. -# -# TSort requires two methods to interpret an object as a graph, -# tsort_each_node and tsort_each_child. -# -# * tsort_each_node is used to iterate for all nodes over a graph. -# * tsort_each_child is used to iterate for child nodes of a given node. -# -# The equality of nodes are defined by eql? and hash since -# TSort uses Hash internally. -# -# == A Simple Example -# -# The following example demonstrates how to mix the TSort module into an -# existing class (in this case, Hash). Here, we're treating each key in -# the hash as a node in the graph, and so we simply alias the required -# #tsort_each_node method to Hash's #each_key method. For each key in the -# hash, the associated value is an array of the node's child nodes. This -# choice in turn leads to our implementation of the required #tsort_each_child -# method, which fetches the array of child nodes and then iterates over that -# array using the user-supplied block. -# -# require 'tsort' -# -# class Hash -# include TSort -# alias tsort_each_node each_key -# def tsort_each_child(node, &block) -# fetch(node).each(&block) -# end -# end -# -# {1=>[2, 3], 2=>[3], 3=>[], 4=>[]}.tsort -# #=> [3, 2, 1, 4] -# -# {1=>[2], 2=>[3, 4], 3=>[2], 4=>[]}.strongly_connected_components -# #=> [[4], [2, 3], [1]] -# -# == A More Realistic Example -# -# A very simple `make' like tool can be implemented as follows: -# -# require 'tsort' -# -# class Make -# def initialize -# @dep = {} -# @dep.default = [] -# end -# -# def rule(outputs, inputs=[], &block) -# triple = [outputs, inputs, block] -# outputs.each {|f| @dep[f] = [triple]} -# @dep[triple] = inputs -# end -# -# def build(target) -# each_strongly_connected_component_from(target) {|ns| -# if ns.length != 1 -# fs = ns.delete_if {|n| Array === n} -# raise TSort::Cyclic.new("cyclic dependencies: #{fs.join ', '}") -# end -# n = ns.first -# if Array === n -# outputs, inputs, block = n -# inputs_time = inputs.map {|f| File.mtime f}.max -# begin -# outputs_time = outputs.map {|f| File.mtime f}.min -# rescue Errno::ENOENT -# outputs_time = nil -# end -# if outputs_time == nil || -# inputs_time != nil && outputs_time <= inputs_time -# sleep 1 if inputs_time != nil && inputs_time.to_i == Time.now.to_i -# block.call -# end -# end -# } -# end -# -# def tsort_each_child(node, &block) -# @dep[node].each(&block) -# end -# include TSort -# end -# -# def command(arg) -# print arg, "\n" -# system arg -# end -# -# m = Make.new -# m.rule(%w[t1]) { command 'date > t1' } -# m.rule(%w[t2]) { command 'date > t2' } -# m.rule(%w[t3]) { command 'date > t3' } -# m.rule(%w[t4], %w[t1 t3]) { command 'cat t1 t3 > t4' } -# m.rule(%w[t5], %w[t4 t2]) { command 'cat t4 t2 > t5' } -# m.build('t5') -# -# == Bugs -# -# * 'tsort.rb' is wrong name because this library uses -# Tarjan's algorithm for strongly connected components. -# Although 'strongly_connected_components.rb' is correct but too long. -# -# == References -# -# R. E. Tarjan, "Depth First Search and Linear Graph Algorithms", -# <em>SIAM Journal on Computing</em>, Vol. 1, No. 2, pp. 146-160, June 1972. -# - -module TSort - class Cyclic < StandardError - end - - # - # Returns a topologically sorted array of nodes. - # The array is sorted from children to parents, i.e. - # the first element has no child and the last node has no parent. - # - # If there is a cycle, TSort::Cyclic is raised. - # - def tsort - result = [] - tsort_each {|element| result << element} - result - end - - # - # The iterator version of the #tsort method. - # <tt><em>obj</em>.tsort_each</tt> is similar to <tt><em>obj</em>.tsort.each</tt>, but - # modification of _obj_ during the iteration may lead to unexpected results. - # - # #tsort_each returns +nil+. - # If there is a cycle, TSort::Cyclic is raised. - # - def tsort_each # :yields: node - each_strongly_connected_component {|component| - if component.size == 1 - yield component.first - else - raise Cyclic.new("topological sort failed: #{component.inspect}") - end - } - end - - # - # Returns strongly connected components as an array of arrays of nodes. - # The array is sorted from children to parents. - # Each elements of the array represents a strongly connected component. - # - def strongly_connected_components - result = [] - each_strongly_connected_component {|component| result << component} - result - end - - # - # The iterator version of the #strongly_connected_components method. - # <tt><em>obj</em>.each_strongly_connected_component</tt> is similar to - # <tt><em>obj</em>.strongly_connected_components.each</tt>, but - # modification of _obj_ during the iteration may lead to unexpected results. - # - # - # #each_strongly_connected_component returns +nil+. - # - def each_strongly_connected_component # :yields: nodes - id_map = {} - stack = [] - tsort_each_node {|node| - unless id_map.include? node - each_strongly_connected_component_from(node, id_map, stack) {|c| - yield c - } - end - } - nil - end - - # - # Iterates over strongly connected component in the subgraph reachable from - # _node_. - # - # Return value is unspecified. - # - # #each_strongly_connected_component_from doesn't call #tsort_each_node. - # - def each_strongly_connected_component_from(node, id_map={}, stack=[]) # :yields: nodes - minimum_id = node_id = id_map[node] = id_map.size - stack_length = stack.length - stack << node - - tsort_each_child(node) {|child| - if id_map.include? child - child_id = id_map[child] - minimum_id = child_id if child_id && child_id < minimum_id - else - sub_minimum_id = - each_strongly_connected_component_from(child, id_map, stack) {|c| - yield c - } - minimum_id = sub_minimum_id if sub_minimum_id < minimum_id - end - } - - if node_id == minimum_id - component = stack.slice!(stack_length .. -1) - component.each {|n| id_map[n] = nil} - yield component - end - - minimum_id - end - - # - # Should be implemented by a extended class. - # - # #tsort_each_node is used to iterate for all nodes over a graph. - # - def tsort_each_node # :yields: node - raise NotImplementedError.new - end - - # - # Should be implemented by a extended class. - # - # #tsort_each_child is used to iterate for child nodes of _node_. - # - def tsort_each_child(node) # :yields: child - raise NotImplementedError.new - end -end - -if __FILE__ == $0 - require 'test/unit' - - class TSortHash < Hash # :nodoc: - include TSort - alias tsort_each_node each_key - def tsort_each_child(node, &block) - fetch(node).each(&block) - end - end - - class TSortArray < Array # :nodoc: - include TSort - alias tsort_each_node each_index - def tsort_each_child(node, &block) - fetch(node).each(&block) - end - end - - class TSortTest < Test::Unit::TestCase # :nodoc: - def test_dag - h = TSortHash[{1=>[2, 3], 2=>[3], 3=>[]}] - assert_equal([3, 2, 1], h.tsort) - assert_equal([[3], [2], [1]], h.strongly_connected_components) - end - - def test_cycle - h = TSortHash[{1=>[2], 2=>[3, 4], 3=>[2], 4=>[]}] - assert_equal([[4], [2, 3], [1]], - h.strongly_connected_components.map {|nodes| nodes.sort}) - assert_raise(TSort::Cyclic) { h.tsort } - end - - def test_array - a = TSortArray[[1], [0], [0], [2]] - assert_equal([[0, 1], [2], [3]], - a.strongly_connected_components.map {|nodes| nodes.sort}) - - a = TSortArray[[], [0]] - assert_equal([[0], [1]], - a.strongly_connected_components.map {|nodes| nodes.sort}) - end - end - -end - |