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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/advent2020/2a.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
# start = parse-int(slice)
var _start/eax: int <- parse-decimal-int-from-slice slice
var start/ebx: int <- copy _start
var dash/eax: byte <- read-byte line # skip '-'
# slice = next-token(line, ' ')
next-token line, 0x20, slice
var _end/eax: int <- parse-decimal-int-from-slice slice
var end/esi: int <- copy _end
print-int32-decimal 0, start
print-string 0, " "
print-int32-decimal 0, end
print-string 0, "\n"
# 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? start, end, 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
}
fn valid? start: int, end: int, letter: byte, password: (addr stream byte) -> _/eax: boolean {
var letter-count/edi: int <- copy 0
# for every c in password
# if (c == letter)
# ++letter-count
{
var done?/eax: boolean <- stream-empty? password
compare done?, 0/false
break-if-!=
var c/eax: byte <- read-byte password
compare c, letter
{
break-if-!=
letter-count <- increment
}
loop
}
# return (start <= letter-count <= end)
compare letter-count, start
{
break-if->=
return 0/false
}
compare letter-count, end
{
break-if-<=
return 0/false
}
return 1/true
}
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