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p23/main.jl

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+include("./../util/julia/erastothenes_extended_sieve.jl")
+import .erastothenes_extended_sieve: extended_sieve, get_extended_sieve, run!
+import Combinatorics: multiset_combinations
+
+function answer(max)
+    b = BitVector(undef, max)
+    
+    a = Vector{Int}(undef, 0)
+    
+    s = get_extended_sieve()
+    run!(s, max)
+
+    for i ∈ 1:max
+        if ~s.sieve.sieve[i] && is_abundant(s.factors[i])
+            push!(a, i)
+        end
+    end
+    
+    for i ∈ a
+        for j ∈ a
+            if i+j <= max
+                b[i+j] = true
+            end
+        end
+    end
+
+    sum = 0
+    for i ∈ 1:max
+        if ~b[i]
+            sum += i
+        end
+    end
+    
+    return sum
+end
+
+function is_abundant(V)
+    n = length(V)
+    sum = 1
+    for i ∈ 1:n-1
+        for j ∈ multiset_combinations(V, i)
+            sum += prod(j)
+        end
+    end
+    return sum > prod(V)
+end