Day 04 part two

Signed-off-by: Christopher Arndt <chris@chrisarndt.de>

day_04/solution_04b.nim

@@ -0,0 +1,51 @@
+import std/[cmdline, sequtils, setutils, strformat, strscans, strutils]
+
+var result = 0
+var fn = if paramCount() > 0: paramStr(1) else: "input_04.txt"
+var lines = readFile(fn).strip.splitLines
+
+# ASSUMPTION: lottery numbers are < 128
+type
+    Card = ref object
+        idx: int
+        play, pot: set[int8]
+var cards: seq[Card]
+
+proc value(card: Card): int =
+    (card.play * card.pot).len
+
+#proc `$`(card: Card): string =
+#    return &"Card idx={card.idx}: value={card.value}"
+
+
+for i, line in lines:
+    var cardno: int
+    let cardspec = line.split(":", 1)
+
+    if scanf(cardspec[0].strip, "Card$s$i", cardno):
+        let card = new Card
+        card.idx = i
+        card.play = cardspec[1].split("|")[0].strip.splitWhitespace().mapIt(it.strip).mapIt(it.parseInt).mapIt(it.int8).toSet
+        card.pot = cardspec[1].split("|")[1].strip.splitWhitespace().mapIt(it.strip).mapIt(it.parseInt).mapIt(it.int8).toSet
+        #echo &"Card {card.idx}: {card.play}, {card.pot} => {card.value}"
+        cards.add(card)
+
+var stack = cards
+while stack.len > 0:
+    result += len(stack)
+    var extra_cards: seq[Card]
+
+    for card in stack:
+        if card.value > 0:
+            extra_cards.add(cards[card.idx + 1..min(card.idx + card.value, cards.len - 1)])
+
+    stack = extra_cards
+
+#echo &"Cards processed: {cards.len}"
+echo &"Result: {result}"
+
+case fn:
+    of "input_04.txt":
+        assert result == 11787590
+    of "sample_input_04.txt":
+        assert result == 30