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# https://adventofcode.com/2020/day/2
#
# To run (on Linux):
# $ git clone https://github.com/akkartik/mu
# $ cd mu
# $ ./translate apps/advent2020/2b.mu
# $ ./a.elf < input
#
# You'll need to register to download the 'input' file for yourself.
fn main -> _/ebx: int {
var valid-password-count/edi: int <- copy 0
var line-storage: (stream byte 0x100) # 256 bytes
var line/edx: (addr stream byte) <- address line-storage
var slice-storage: slice
var slice/ecx: (addr slice) <- address slice-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-!=
print-stream-to-real-screen line
# slice = next-token(line, '-')
next-token line, 0x2d, slice
# pos1 = parse-int(slice)
var _pos1/eax: int <- parse-decimal-int-from-slice slice
var pos1/ebx: int <- copy _pos1
var dash/eax: byte <- read-byte line # skip '-'
# slice = next-token(line, ' ')
next-token line, 0x20, slice
var _pos2/eax: int <- parse-decimal-int-from-slice slice
var pos2/esi: int <- copy _pos2
print-int32-decimal 0, pos1
print-string 0, " "
print-int32-decimal 0, pos2
print-string 0, "\n"
compare pos1, pos2
{
break-if-<=
print-string 0, "out of order!\n"
return 1
}
# letter = next non-space
skip-chars-matching-whitespace line
var letter/eax: byte <- read-byte line
# skip some stuff
{
var colon/eax: byte <- read-byte line # skip ':'
}
skip-chars-matching-whitespace line
# now check the rest of the line
var valid?/eax: boolean <- valid? pos1, pos2, letter, line
compare valid?, 0/false
{
break-if-=
print-string 0, "valid!\n"
valid-password-count <- increment
}
loop
}
print-int32-decimal 0, valid-password-count
print-string 0, "\n"
return 0
}
# ideally password would be a random-access array
# we'll just track an index
# one benefit: we can easily start at 1
fn valid? pos1: int, pos2: int, letter: byte, password: (addr stream byte) -> _/eax: boolean {
var i/esi: int <- copy 1
var letter-count/edi: int <- copy 0
# while password stream isn't empty
# c = read byte from password
# if (c == letter)
# if (i == pos1)
# ++letter-count
# if (i == pos2)
# ++letter-count
# ++i
{
#? print-string 0, " "
#? print-int32-decimal 0, i
#? print-string 0, "\n"
var done?/eax: boolean <- stream-empty? password
compare done?, 0/false
break-if-!=
var c/eax: byte <- read-byte password
#? {
#? var c2/eax: int <- copy c
#? print-int32-decimal 0, c2
#? print-string 0, "\n"
#? }
compare c, letter
{
break-if-!=
compare i, pos1
{
break-if-!=
letter-count <- increment
#? print-string 0, " hit\n"
}
compare i, pos2
{
break-if-!=
letter-count <- increment
#? print-string 0, " hit\n"
}
}
i <- increment
loop
}
# return (letter-count == 1)
compare letter-count, 1
{
break-if-!=
return 1/true
}
return 0/false
}
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