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# https://adventofcode.com/2020/day/1
#
# To run (on Linux):
# $ git clone https://github.com/akkartik/mu
# $ cd mu
# $ ./translate_mu apps/advent2020/1b.mu
# $ ./a.elf < input
# found
# 143 407 1470
# 85555470
#
# You'll need to register to download the 'input' file for yourself.
fn main -> _/ebx: int {
# data structure
var numbers-storage: (array int 0x100) # 256 ints
var numbers/esi: (addr array int) <- address numbers-storage
var numbers-index/ecx: int <- copy 0
# phase 1: parse each line from stdin and add it to numbers
{
var line-storage: (stream byte 0x100) # 256 bytes
var line/edx: (addr stream byte) <- address line-storage
{
#? print-string 0, "== iter\n"
# 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
# convert line to int and append it to numbers
var n/eax: int <- parse-decimal-int-from-stream line
#? print-int32-decimal 0, n
#? print-string 0, "\n"
var dest/ebx: (addr int) <- index numbers, numbers-index
copy-to *dest, n
numbers-index <- increment
#? print-string 0, "== "
#? print-int32-decimal 0, numbers-index
#? print-string 0, "\n"
loop
}
}
# phase 2: for every pair of distinct numbers, check if the rest of the
# array has 2020-it
var i/edi: int <- copy 0
{
compare i, numbers-index
break-if->=
# for j from i+1 to end
var j/edx: int <- copy i
j <- increment
{
compare j, numbers-index
break-if->=
{
compare i, j
break-if-=
var target/ebx: int <- copy 0x7e4 # 2020
var src/edi: (addr int) <- index numbers, i
target <- subtract *src
var src2/ecx: (addr int) <- index numbers, j
target <- subtract *src2
{
var found?/eax: boolean <- find-after numbers, j, target
compare found?, 0 # false
break-if-=
print-string 0, "found\n"
print-int32-decimal 0, *src
print-string 0, " "
print-int32-decimal 0, *src2
print-string 0, " "
print-int32-decimal 0, target
print-string 0, "\n"
target <- multiply *src
target <- multiply *src2
print-int32-decimal 0, target
print-string 0, "\n"
return 0 # success
}
}
j <- increment
loop
}
i <- increment
loop
}
return 1 # not found
}
fn find-after _numbers: (addr array int), start: int, _target: int -> _/eax: boolean {
var numbers/esi: (addr array int) <- copy _numbers
var target/edi: int <- copy _target
var len/ecx: int <- length numbers
var i/eax: int <- copy start
i <- increment
{
compare i, len
break-if->=
var src/edx: (addr int) <- index numbers, i
# if *src == target, return true
compare *src, target
{
break-if-!=
return 1 # true
}
i <- increment
loop
}
return 0 # false
}
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