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Pull Request for Issue #719 #723

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Pull Request for Issue #719 #723

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2b7efc5
Update disjoint_set.jl
NehaDalmia Jan 21, 2021
8d0cad7
Update src/disjoint_set.jl
NehaDalmia Jan 21, 2021
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56 changes: 30 additions & 26 deletions src/disjoint_set.jl
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
# Disjoint-Set
#Disjoint-Set
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############################################################
#
Expand All @@ -12,12 +12,20 @@
# to an integer index
#
############################################################

_intdisjointset_bounds_err_msg(T) = "the maximum number of elements in IntDisjointSet{$T} is $(typemax(T))"

abstract type Scalarness end
struct Scalar <: Scalarness end
struct NotScalar <: Scalarness end

isscalar(::Type{Any}) = NotScalar() # if we don't know the type we can't really know if scalar or not
isscalar(::Type{<:AbstractString}) = NotScalar() # We consider strings to be nonscalar
isscalar(::Type{<:Number}) = Scalar() # We consider Numbers to be scalar
isscalar(::Type{Char}) = Scalar() # We consider Character to be scalar
isscalar(::Type{Symbol}) = Scalar()
isscalar(::Type{T}) where T = hasmethod(iterate, (T,)) ? NotScalar() : Scalar()
"""
IntDisjointSet{T<:Integer}(n::Integer)

A forest of disjoint sets of integers, which is a data structure
(also called a union–find data structure or merge–find set)
that tracks a set of elements partitioned
Expand All @@ -35,7 +43,6 @@ Base.length(s::IntDisjointSet) = length(s.parents)

"""
num_groups(s::IntDisjointSet)

Get a number of groups.
"""
num_groups(s::IntDisjointSet) = s.ngroups
Expand All @@ -62,22 +69,19 @@ end

"""
find_root!(s::IntDisjointSet{T}, x::T)

Find the root element of the subset that contains an member x.
Path compression is implemented here.
"""
find_root!(s::IntDisjointSet{T}, x::T) where {T<:Integer} = find_root_impl!(s.parents, x)

"""
in_same_set(s::IntDisjointSet{T}, x::T, y::T)

Returns `true` if `x` and `y` belong to the same subset in `s` and `false` otherwise.
"""
in_same_set(s::IntDisjointSet{T}, x::T, y::T) where {T<:Integer} = find_root!(s, x) == find_root!(s, y)

"""
union!(s::IntDisjointSet{T}, x::T, y::T)

Merge the subset containing x and that containing y into one
and return the root of the new set.
"""
Expand All @@ -90,7 +94,6 @@ end

"""
root_union!(s::IntDisjointSet{T}, x::T, y::T)

Form a new set that is the union of the two sets whose root elements are
x and y and return the root of the new set.
Assume x ≠ y (unsafe).
Expand All @@ -113,7 +116,6 @@ end

"""
push!(s::IntDisjointSet{T})

Make a new subset with an automatically chosen new element x.
Returns the new element. Throw an `ArgumentError` if the
capacity of the set would be exceeded.
Expand All @@ -130,30 +132,36 @@ end

"""
DisjointSet{T}(xs)

A forest of disjoint sets of arbitrary value type T.

It is a wrapper of IntDisjointSet{Int}, which uses a
dictionary to map the input value to an internal index.
"""
mutable struct DisjointSet{T} <: AbstractSet{T}
intmap::Dict{T,Int}
revmap::Vector{T}
internal::IntDisjointSet{Int}

DisjointSet{T}() where T = new{T}(Dict{T,Int}(), Vector{T}(), IntDisjointSet(0))

function DisjointSet{T}(xs) where T # xs must be iterable
imap = Dict{T,Int}()
rmap = Vector{T}()
n = length(xs)
sizehint!(imap, n)
sizehint!(rmap, n)
id = 0
for x in xs
imap[x] = (id += 1)
push!(rmap,x)
if(typeof(isscalar(typeof(xs)))!=Scalar)
n = length(xs)
sizehint!(imap, n)
sizehint!(rmap, n)
id = 0
for x in xs
imap[x] = (id += 1)
push!(rmap,x)
end
new{T}(imap, rmap, IntDisjointSet(n))
else
id = 0
imap[xs] = (id += 1)
push!(rmap,xs)
new{T}(imap, rmap, IntDisjointSet(1))

end
new{T}(imap, rmap, IntDisjointSet(n))
end
end

Expand All @@ -173,7 +181,6 @@ Base.length(s::DisjointSet) = length(s.internal)

"""
num_groups(s::DisjointSet)

Get a number of groups.
"""
num_groups(s::DisjointSet) = num_groups(s.internal)
Expand All @@ -187,40 +194,37 @@ end

"""
find_root!{T}(s::DisjointSet{T}, x::T)

Finds the root element of the subset in `s` which has the element `x` as a member.
"""
find_root!(s::DisjointSet{T}, x::T) where {T} = s.revmap[find_root!(s.internal, s.intmap[x])]

"""
in_same_set(s::DisjointSet{T}, x::T, y::T)

Returns `true` if `x` and `y` belong to the same subset in `s` and `false` otherwise.
"""
in_same_set(s::DisjointSet{T}, x::T, y::T) where {T} = in_same_set(s.internal, s.intmap[x], s.intmap[y])

"""
union!(s::DisjointSet{T}, x::T, y::T)

Merge the subset containing x and that containing y into one
and return the root of the new set.
"""
Base.union!(s::DisjointSet{T}, x::T, y::T) where {T} = s.revmap[union!(s.internal, s.intmap[x], s.intmap[y])]

"""
root_union!(s::DisjointSet{T}, x::T, y::T)

Form a new set that is the union of the two sets whose root elements are
x and y and return the root of the new set.
Assume x ≠ y (unsafe).
"""
root_union!(s::DisjointSet{T}, x::T, y::T) where {T} = s.revmap[root_union!(s.internal, s.intmap[x], s.intmap[y])]

"""
push!(s::DisjointSet{T}, x::T)

push!(s::DisjointSet{T}, x::T)
Make a new subset with an automatically chosen new element x.
Returns the new element.

"""
function Base.push!(s::DisjointSet{T}, x::T) where T
haskey(s.intmap, x) && return x
Expand Down