98 lines
2.7 KiB
Forth
98 lines
2.7 KiB
Forth
# https://adventofcode.com/2020/day/1
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#
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# To run (on Linux):
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# $ git clone https://github.com/akkartik/mu
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# $ cd mu
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# $ ./translate advent2020/1a.mu
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# $ ./a.elf < input
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# found
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# 1353 667
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# 902451
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#
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# You'll need to register to download the 'input' file for yourself.
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fn main -> _/ebx: int {
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# data structure
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var numbers-storage: (array int 0x100) # 256 ints
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var numbers/esi: (addr array int) <- address numbers-storage
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var numbers-index/ecx: int <- copy 0
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# phase 1: parse each line from stdin and add it to numbers
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{
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var line-storage: (stream byte 0x100) # 256 bytes
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var line/edx: (addr stream byte) <- address line-storage
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{
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#? print-string 0, "== iter\n"
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# read line from stdin
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clear-stream line
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read-line-from-real-keyboard line
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# if line is empty (not even a newline), quit
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var done?/eax: boolean <- stream-empty? line
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compare done?, 0/false
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break-if-!=
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#? print-stream-to-real-screen line
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# convert line to int and append it to numbers
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var n/eax: int <- parse-decimal-int-from-stream line
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#? print-int32-decimal 0, n
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#? print-string 0, "\n"
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var dest/ebx: (addr int) <- index numbers, numbers-index
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copy-to *dest, n
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numbers-index <- increment
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#? print-string 0, "== "
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#? print-int32-decimal 0, numbers-index
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#? print-string 0, "\n"
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loop
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}
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}
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# phase 2: for each number in the array, check if 2020-it is in the rest of
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# the array
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var i/eax: int <- copy 0
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{
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compare i, numbers-index
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break-if->=
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var src/ebx: (addr int) <- index numbers, i
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#? print-int32-decimal 0, *src
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#? print-string 0, "\n"
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var target/ecx: int <- copy 0x7e4 # 2020
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target <- subtract *src
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{
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var found?/eax: boolean <- find-after numbers, i, target
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compare found?, 0/false
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break-if-=
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print-string 0, "found\n"
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print-int32-decimal 0, *src
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print-string 0, " "
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print-int32-decimal 0, target
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print-string 0, "\n"
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target <- multiply *src
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print-int32-decimal 0, target
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print-string 0, "\n"
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return 0/success
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}
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i <- increment
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loop
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}
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return 1/not-found
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}
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fn find-after _numbers: (addr array int), start: int, _target: int -> _/eax: boolean {
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var numbers/esi: (addr array int) <- copy _numbers
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var target/edi: int <- copy _target
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var len/ecx: int <- length numbers
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var i/eax: int <- copy start
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i <- increment
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{
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compare i, len
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break-if->=
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var src/edx: (addr int) <- index numbers, i
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# if *src == target, return true
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compare *src, target
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{
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break-if-!=
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return 1/true
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}
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i <- increment
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loop
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}
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return 0/false
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}
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