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:heavy_check_mark: src/graph/re_rooting.cr

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Code

require "../graph"

# Example of `T`:
# ```
# struct DP
#   getter val : Int64, cnt : Int32
#
#   def initialize
#     @val, @cnt = 0i64, 0
#   end
#
#   def initialize(@val, @cnt)
#   end
#
#   def +(other : self) : self
#     DP.new(val + other.val, cnt + other.cnt)
#   end
#
#   def add_root(v : Int32) : self
#     DP.new(val + cnt, cnt + 1)
#   end
# end
# ```
class ReRooting(T, GraphType)
  getter graph : GraphType

  def initialize(size : Int)
    initialize(GraphType.new(size))
  end

  def initialize(@graph : GraphType)
    @dp = Array(Array(T)).new
    @result = Array(T).new
  end

  def initialize(size : Int, edges : Enumerable)
    initialize(GraphType.new(size, edges))
  end

  delegate size, :<<, add_edges, to: @graph

  private def dfs(v : Int32, p : Int32) : T
    acc = T.new
    graph[v].each_with_index do |edge, i|
      if edge.to != p
        acc += (@dp[v][i] = dfs(edge.to, v))
      end
    end
    acc.add_root(v)
  end

  private def bfs(v : Int32, p : Int32, dp_p : T) : Nil
    graph[v].each_with_index do |edge, i|
      @dp[v][i] = dp_p if edge.to == p
    end

    n = graph[v].size
    dp_left = Array.new(n + 1, T.new)
    (0...n).each do |i|
      dp_left[i + 1] = dp_left[i] + @dp[v][i]
    end
    dp_right = Array.new(n + 1, T.new)
    (0...n).reverse_each do |i|
      dp_right[i] = dp_right[i + 1] + @dp[v][i]
    end
    @result[v] = dp_left.last.add_root(v)

    graph[v].each_with_index do |edge, i|
      bfs(edge.to, v, (dp_left[i] + dp_right[i + 1]).add_root(v)) if edge.to != p
    end
  end

  def solve : Array(T)
    @dp = Array.new(size) { |i| Array.new(@graph[i].size, T.new) }
    @result = Array.new(size, T.new)
    dfs(0, -1)
    bfs(0, -1, T.new)
    @result
  end
end
# require "../graph"
# require "./graph/edge"
struct WeightedEdge(T)
  include Comparable(WeightedEdge(T))

  property to : Int32, cost : T

  def initialize(@to, @cost : T)
  end

  def <=>(other : WeightedEdge(T))
    {cost, to} <=> {other.cost, other.to}
  end

  def to_s(io) : Nil
    io << '(' << to << ", " << cost << ')'
  end

  def inspect(io) : Nil
    io << "->" << to << '(' << cost << ')'
  end
end

struct WeightedEdge2(T)
  include Comparable(WeightedEdge2(T))

  property from : Int32, to : Int32, cost : T

  def initialize(@from, @to, @cost : T)
  end

  def initialize(@from, edge : WeightedEdge(T))
    @to, @cost = edge.to, edge.cost
  end

  def <=>(other : WeightedEdge2(T))
    {cost, from, to} <=> {other.cost, other.from, other.to}
  end

  def reverse : self
    WeightedEdge2(T).new(to, from, cost)
  end

  def sort : self
    WeightedEdge2(T).new(*{to, from}.minmax, cost)
  end

  def to_s(io) : Nil
    io << '(' << from << ", " << to << ", " << cost << ')'
  end

  def inspect(io) : Nil
    io << from << "->" << to << '(' << cost << ')'
  end
end

struct UnweightedEdge
  property to : Int32

  def initialize(@to)
  end

  def initialize(@to, cost)
  end

  def cost : Int32
    1
  end

  def to_s(io) : Nil
    io << to
  end

  def inspect(io) : Nil
    io << "->" << to
  end
end

struct UnweightedEdge2
  property from : Int32, to : Int32

  def initialize(@from, @to)
  end

  def initialize(@from, @to, cost)
  end

  def initialize(@from, edge : UnweightedEdge)
    @to = edge.to
  end

  def cost : Int32
    1
  end

  def reverse : self
    UnweightedEdge2.new(to, from)
  end

  def sort : self
    UnweightedEdge2.new(*{to, from}.minmax)
  end

  def to_s(io) : Nil
    io << '(' << from << ", " << to << ')'
  end

  def inspect(io) : Nil
    io << from << "->" << to
  end
end

module Graph(Edge, Edge2)
  include Enumerable(Edge2)

  getter graph : Array(Array(Edge))

  def initialize(size : Int)
    @graph = Array(Array(Edge)).new(size) { [] of Edge }
  end

  def initialize(size : Int, edges : Enumerable)
    initialize(size)
    add_edges(edges)
  end

  # Add *edge*.
  abstract def <<(edge : Edge2)

  # :ditto:
  def <<(edge : Tuple) : self
    self << Edge2.new(*edge)
  end

  def add_edges(edges : Enumerable) : self
    edges.each { |edge| self << edge }
    self
  end

  delegate size, :[], to: @graph

  # Yields each edge of the graph, ans returns `nil`.
  def each(&) : Nil
    (0...size).each do |v|
      graph[v].each do |edge|
        yield Edge2.new(v, edge)
      end
    end
  end

  def each_child(vertex : Int, parent, &block) : Nil
    graph[vertex].each do |edge|
      yield edge if edge.to != parent
    end
  end

  def each_child(vertex : Int, parent)
    graph[vertex].each.reject(&.to.== parent)
  end

  def reverse : self
    if self.class.directed?
      each_with_object(self.class.new(size)) do |edge, reversed|
        reversed << edge.reverse
      end
    else
      dup
    end
  end

  def to_undirected : self
    if self.class.directed?
      each_with_object(self.class.new(size)) do |edge, graph|
        graph << edge << edge.reverse
      end
    else
      dup
    end
  end

  def to_s(io : IO) : Nil
    io << '['
    join(", ", io) do |edge, io|
      edge.inspect io
    end
    io << ']'
  end

  def inspect(io : IO) : Nil
    io << "[\n"
    graph.each do |edges|
      io << "  " << edges << ",\n"
    end
    io << ']'
  end
end

class DiGraph(T)
  include Graph(WeightedEdge(T), WeightedEdge2(T))

  def self.weighted?
    true
  end

  def self.directed?
    true
  end

  def initialize(size : Int)
    super
  end

  def initialize(size : Int, edges : Enumerable(WeightedEdge2(T)))
    super
  end

  def initialize(size : Int, edges : Enumerable({Int32, Int32, T}))
    super
  end

  def <<(edge : WeightedEdge2(T)) : self
    raise IndexError.new unless 0 <= edge.from < size && 0 <= edge.to < size
    @graph[edge.from] << WeightedEdge.new(edge.to, edge.cost)
    self
  end
end

class UnGraph(T)
  include Graph(WeightedEdge(T), WeightedEdge2(T))

  def self.weighted?
    true
  end

  def self.directed?
    false
  end

  def initialize(size : Int)
    super
  end

  def initialize(size : Int, edges : Enumerable(WeightedEdge2(T)))
    super
  end

  def initialize(size : Int, edges : Enumerable({Int32, Int32, T}))
    super
  end

  def <<(edge : WeightedEdge2(T)) : self
    raise IndexError.new unless 0 <= edge.from < size && 0 <= edge.to < size
    @graph[edge.from] << WeightedEdge.new(edge.to, edge.cost)
    @graph[edge.to] << WeightedEdge.new(edge.from, edge.cost)
    self
  end
end

class UnweightedDiGraph
  include Graph(UnweightedEdge, UnweightedEdge2)

  def self.weighted?
    false
  end

  def self.directed?
    true
  end

  def initialize(size : Int)
    super
  end

  def initialize(size : Int, edges : Enumerable)
    super
  end

  def <<(edge : UnweightedEdge2) : self
    raise IndexError.new unless 0 <= edge.from < size && 0 <= edge.to < size
    @graph[edge.from] << UnweightedEdge.new(edge.to)
    self
  end
end

class UnweightedUnGraph
  include Graph(UnweightedEdge, UnweightedEdge2)

  def self.weighted?
    false
  end

  def self.directed?
    false
  end

  def initialize(size : Int)
    super
  end

  def initialize(size : Int, edges : Enumerable)
    super
  end

  def <<(edge : UnweightedEdge2) : self
    raise IndexError.new unless 0 <= edge.from < size && 0 <= edge.to < size
    @graph[edge.from] << UnweightedEdge.new(edge.to)
    @graph[edge.to] << UnweightedEdge.new(edge.from)
    self
  end
end

# Example of `T`:
# ```
# struct DP
#   getter val : Int64, cnt : Int32
#
#   def initialize
#     @val, @cnt = 0i64, 0
#   end
#
#   def initialize(@val, @cnt)
#   end
#
#   def +(other : self) : self
#     DP.new(val + other.val, cnt + other.cnt)
#   end
#
#   def add_root(v : Int32) : self
#     DP.new(val + cnt, cnt + 1)
#   end
# end
# ```
class ReRooting(T, GraphType)
  getter graph : GraphType

  def initialize(size : Int)
    initialize(GraphType.new(size))
  end

  def initialize(@graph : GraphType)
    @dp = Array(Array(T)).new
    @result = Array(T).new
  end

  def initialize(size : Int, edges : Enumerable)
    initialize(GraphType.new(size, edges))
  end

  delegate size, :<<, add_edges, to: @graph

  private def dfs(v : Int32, p : Int32) : T
    acc = T.new
    graph[v].each_with_index do |edge, i|
      if edge.to != p
        acc += (@dp[v][i] = dfs(edge.to, v))
      end
    end
    acc.add_root(v)
  end

  private def bfs(v : Int32, p : Int32, dp_p : T) : Nil
    graph[v].each_with_index do |edge, i|
      @dp[v][i] = dp_p if edge.to == p
    end

    n = graph[v].size
    dp_left = Array.new(n + 1, T.new)
    (0...n).each do |i|
      dp_left[i + 1] = dp_left[i] + @dp[v][i]
    end
    dp_right = Array.new(n + 1, T.new)
    (0...n).reverse_each do |i|
      dp_right[i] = dp_right[i + 1] + @dp[v][i]
    end
    @result[v] = dp_left.last.add_root(v)

    graph[v].each_with_index do |edge, i|
      bfs(edge.to, v, (dp_left[i] + dp_right[i + 1]).add_root(v)) if edge.to != p
    end
  end

  def solve : Array(T)
    @dp = Array.new(size) { |i| Array.new(@graph[i].size, T.new) }
    @result = Array.new(size, T.new)
    dfs(0, -1)
    bfs(0, -1, T.new)
    @result
  end
end
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