[Julia] Day 12 (#52)

inputs/12_example.txt

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+???.### 1,1,3
+.??..??...?##. 1,1,3
+?#?#?#?#?#?#?#? 1,3,1,6
+????.#...#... 4,1,1
+????.######..#####. 1,6,5
+?###???????? 3,2,1

solutions/12_example.txt

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+21
+525152

solutions/12_moelf.txt

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+7173
+29826669191291

src/julia/12_moelf.jl

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+const CACHE = Dict()
+
+function rec_count(str, intvec)
+    get!(CACHE, (str, intvec)) do
+        if isempty(intvec)
+            # no group left, illegal to have any '#'
+            all(!=('#'), str)
+        elseif sum(intvec) > length(str)
+            # not enough chars left to form all groups
+            0
+        elseif first(str) == '.'
+            rec_count(str[2:end], intvec)
+        else
+            count = 0
+            if first(str) == '?'
+                count += rec_count(str[2:end], intvec)
+            end
+            N = first(intvec)
+            # first N is mix of "#?"
+            # followed by a '.'
+            stub = get(str, N + 1, '.')
+            if all(!=('.'), first(str, N)) && stub != '#'
+                count += rec_count(str[N+2:end], intvec[2:end])
+            end
+            count
+        end
+    end
+end
+
+function impl(pairs, N)
+    sum(pairs) do (str, intvec)
+        str, intvec = join(fill(str, N), '?'), repeat(intvec, N)
+        rec_count(str, intvec)
+    end
+end
+
+function main(path)
+    lines = map(eachline(path)) do l
+        str, int_str = split(l)
+        intvec = parse.(Int, split(int_str, ","))
+        (str, intvec)
+    end
+    println(impl(lines, 1))
+    println(impl(lines, 5))
+end
+
+(abspath(PROGRAM_FILE) == @__FILE__) && main(ARGS[1])