2023 day 4

2023/day04-scratchcards/day04.jl

@@ -0,0 +1,52 @@
+function readcards(filename)
+    Channel() do ch
+        for line in eachline(filename)
+            r = split(line, "|")
+            l = split(r[1])[3:end]
+            m = split(r[2])
+            put!(ch, (map(x->parse(Int32, x), l),
+                      map(x->parse(Int32, x), m)))
+        end
+    end
+end
+
+
+function nwin(winners, card)
+    score = 0
+    for winner in winners
+        if winner ∈ card
+            score += 1
+        end
+    end
+    score
+end
+
+
+function score(winners, card)
+    let s = nwin(winners, card)
+        if s > 0
+            2^(s-1)
+        else
+            0
+        end
+    end
+end
+
+
+let allcards = collect(readcards("input"))
+
+    println("Part 1: ", sum(map(x->score(x[1],x[2]), allcards)))
+
+    let pending = [1 for _ in allcards], ncards = 0
+        for card in allcards
+            ncopies = popfirst!(pending)
+            ncards += ncopies
+            nmatch = nwin(card[1], card[2])
+            for i in 1:nmatch
+                pending[i] += ncopies
+            end
+        end
+        println("Part 2: ", ncards)
+    end
+
+end