day 4 tcl solution

day04/sol.tcl

@@ -0,0 +1,28 @@
+#!/usr/bin/env tclsh
+source ../prelude.tcl
+package require struct::set
+set input stdin
+
+set part1 0
+while {[gets $input line] >= 0} {
+    regexp {^Card +(\d+): ([\d ]*) \| ([\d ]*)$} $line _ card winners numbers
+    set matches [struct::set intersect $winners $numbers]
+    set score [expr {1 << [llength $matches] >> 1}]
+    incr part1 $score
+
+    incr copies($card)
+    for {set i 0} {$i < [llength $matches]} {incr i} {
+        incr copies([expr {$card+$i+1}]) $copies($card)
+    }
+}
+puts "-"
+puts $part1
+
+foreach {c n} [array get copies] {
+    if {$c > $card} {
+        error "should not have any copies of card $c > $card"
+    }
+}
+
+set part2 [ladd [lmap {card n} [array get copies] {list $n}]]
+puts $part2