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# https://adventofcode.com/2020/day/5
#
# To run (on Linux):
# $ git clone https://github.com/akkartik/mu
# $ cd mu
# $ ./translate apps/advent2020/5b.mu
# $ ./a.elf < input
#
# You'll need to register to download the 'input' file for yourself.
fn main -> _/ebx: int {
var pass-storage: (array int 0x400) # 1k ints
var pass/esi: (addr array int) <- address pass-storage
# phase 1: populate pass array
var line-storage: (stream byte 0x10) # 16 bytes is enough
var line/edx: (addr stream byte) <- address line-storage
{
# read line from stdin
clear-stream line
read-line-from-real-keyboard line
# if line is empty (not even a newline), quit
var done?/eax: boolean <- stream-empty? line
compare done?, 0/false
break-if-!=
# process line
var seat-id/eax: int <- convert-from-binary line
var dest/eax: (addr int) <- index pass, seat-id
copy-to *dest, 1
loop
}
# phase 2: skip empty seats
var i/eax: int <- copy 0
{
compare i, 0x400
break-if->=
var src/ecx: (addr int) <- index pass, i
compare *src, 0
break-if-!=
i <- increment
loop
}
# phase 3: skip non-empty seats
{
compare i, 0x400
break-if->=
var src/ecx: (addr int) <- index pass, i
compare *src, 0
break-if-=
i <- increment
loop
}
print-int32-decimal 0, i
print-string 0, "\n"
return 0
}
fn convert-from-binary in: (addr stream byte) -> _/eax: int {
var result/edi: int <- copy 0
var i/ecx: int <- copy 9 # loop counter and also exponent
{
compare i, 0
break-if-<
var c/eax: byte <- read-byte in
var bit/edx: int <- copy 0
{
compare c, 0x42/B
break-if-!=
bit <- copy 1
}
{
compare c, 0x52/R
break-if-!=
bit <- copy 1
}
var bit-value/eax: int <- repeated-shift-left bit, i
result <- add bit-value
i <- decrement
loop
}
return result
}
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