集合 #

s1 = Set([1, 2, 3, 4, 5])
s2 = Set([1, 2, 2, 3, 3, 3])
s3 = Set{Int}()
s4 = Set()
s5 = Set(["a", "b", "c"])

typeof(Set([1, 2, 3]))
typeof(Set{Int}())
typeof(Set(["a", "b"]))

s = Set([1, 2, 2, 3, 3, 3])
length(s)
collect(s)

s = Set{Int}()
push!(s, 1)
push!(s, 2)
push!(s, 1)
s

s = Set([1, 2, 3, 4, 5])
delete!(s, 3)
pop!(s)
setdiff!(s, Set([1, 2]))
empty!(s)

s = Set([1, 2, 3, 4, 5])
in(3, s)
3 ∈ s
3 ∉ s

s = Set([1, 2, 3, 4, 5])
length(s)
isempty(s)

s1 = Set([1, 2, 3])
s2 = Set([3, 4, 5])
union(s1, s2)
s1 ∪ s2
union!(s1, s2)

s1 = Set([1, 2, 3])
s2 = Set([2, 3, 4])
intersect(s1, s2)
s1 ∩ s2
intersect!(s1, s2)

s1 = Set([1, 2, 3, 4])
s2 = Set([3, 4, 5, 6])
setdiff(s1, s2)
setdiff!(s1, s2)

s1 = Set([1, 2, 3])
s2 = Set([2, 3, 4])
symdiff(s1, s2)

s1 = Set([1, 2])
s2 = Set([1, 2, 3, 4])
issubset(s1, s2)
s1 ⊆ s2
s1 ⊊ s2
s1 ⊈ s2

s1 = Set([1, 2, 3])
s2 = Set([3, 2, 1])
s1 == s2
issetequal(s1, s2)

s = Set([1, 2, 3, 4, 5])
for x in s
    println(x)
end

Set(x^2 for x in 1:5)
Set(x for x in 1:10 if x % 2 == 0)

s = Set([3, 1, 4, 1, 5, 9])
collect(s)
sort(collect(s))

arr = [1, 2, 3, 2, 4, 3, 5, 1]
unique(arr)
collect(Set(arr))

function common_elements(arr1, arr2)
    intersect(Set(arr1), Set(arr2))
end

common_elements([1, 2, 3, 4], [3, 4, 5, 6])

function unique_to_first(arr1, arr2)
    setdiff(Set(arr1), Set(arr2))
end

unique_to_first([1, 2, 3, 4], [3, 4, 5, 6])

function contains_all(container, items)
    issubset(Set(items), Set(container))
end

contains_all([1, 2, 3, 4, 5], [2, 3])
contains_all([1, 2, 3, 4, 5], [2, 6])

using BenchmarkTools

arr = collect(1:10000)
s = Set(arr)

@btime 5000 in $arr
@btime 5000 in $s

bs = BitSet([1, 2, 3, 4, 5])
typeof(bs)

bs = BitSet([1, 2, 3, 4, 5])
push!(bs, 6)
delete!(bs, 3)
3 in bs

using BenchmarkTools

s = Set(1:1000)
bs = BitSet(1:1000)

@btime 500 in $s
@btime 500 in $bs

function find_duplicates(arr)
    seen = Set{eltype(arr)}()
    duplicates = Set{eltype(arr)}()
    for x in arr
        if x in seen
            push!(duplicates, x)
        else
            push!(seen, x)
        end
    end
    return duplicates
end

find_duplicates([1, 2, 3, 2, 4, 3, 5, 1])

function set_cover(universe, subsets)
    remaining = Set(universe)
    selected = []
    
    while !isempty(remaining)
        best = nothing
        best_cover = Set()
        
        for subset in subsets
            cover = intersect(subset, remaining)
            if length(cover) > length(best_cover)
                best = subset
                best_cover = cover
            end
        end
        
        if best === nothing || isempty(best_cover)
            break
        end
        
        push!(selected, best)
        setdiff!(remaining, best)
    end
    
    return selected
end

universe = Set(1:10)
subsets = [Set([1, 2, 3]), Set([3, 4, 5]), Set([5, 6, 7]), Set([7, 8, 9, 10])]
set_cover(universe, subsets)

function unique_words(texts)
    all_words = Set{String}()
    for text in texts
        words = split(lowercase(text))
        for word in words
            push!(all_words, strip(word, ['.', ',', '!', '?']))
        end
    end
    return all_words
end

unique_words(["Hello World", "Hello Julia", "Julia is great"])

function are_anagrams(s1::String, s2::String)
    Set(lowercase(s1)) == Set(lowercase(s2))
end

are_anagrams("listen", "silent")
are_anagrams("hello", "world")