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#!/bin/env tclsh
source lib.tcl
setup 2
puts {Part 1: Count "safe" ordered sequences with intervals such that 1 <= x <= 3.}
proc row_errs {row} {
set report [lassign $row first second]
set neg [expr {abs($second - $first) != ($second - $first)}]
set prev $first
set row_errs 0
foreach num [concat $second $report] {
if {$neg != (abs($num - $prev) != ($num - $prev)) ||
abs($num - $prev) > 3 || abs($num - $prev) < 1} {
incr row_errs
} else {
set prev $num
}
}
return $row_errs
}
foreach report $input {
if ![row_errs $report] { incr safe_count; continue }
# naive, but handles a case like [1 4 2 3] where removing 2 makes it
# safe but an iterative approach only trips on [2]. backtracking
# might be better but idc
for {set i 0} {$i < [llength $report]} {incr i} {
if ![row_errs [lreplace $report $i $i]] {
incr dampened_safe_count
break
}
}
}
incr dampened_safe_count $safe_count
puts "Safe sequence count: $safe_count"
puts ""
puts {Part 2: Tolerate 1 bad entry in a report.}
puts "Dampened sequence count: $dampened_safe_count"
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