first commit

p21/solution.jl

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+include("../util/sieve.jl")
+import .erastothenes_sieve: get_extended_sieve, run, get
+
+function solution(n)
+    s = get_extended_sieve()
+    run(s, n)
+    sum = 0
+    for i = 1:n
+        spds = compute_divisors(i, s)
+        if spds > i
+            spds_2 = compute_divisors(spds, s)
+            if spds_2 == i
+                sum += spds + spds_2
+                println("found pair ", spds, ", ", spds_2)
+            end
+        end
+    end
+    return sum
+end
+
+function compute_divisors(value, s)
+    if value == 1
+        return 1
+    end
+    pvc = get(s, value, false)
+    n = sum(collect(values(pvc[2])))
+    pds = zeros(n)
+    j = 1
+    for key in keys(pvc[2])
+        for i = 1:pvc[2][key]
+            pds[j] = key
+            j += 1
+        end
+    end
+    divisors = Set([])
+    for i = 1:2^n-1
+        prod = 1
+        for j = 0:length(pds)-1
+            if i & (1 << j) > 0
+                prod *= pds[j+1]
+            end
+        end
+        push!(divisors, prod)
+    end
+    return round(Int, sum(collect(divisors)) + 1 - value)
+end
+
+println(solution(10000))