# https://adventofcode.com/2020/day/3 # # To run (on Linux): # $ git clone https://github.com/akkartik/mu # $ cd mu # $ ./translate_mu apps/advent2020/3a.mu # $ ./a.elf < input # # You'll need to register to download the 'input' file for yourself. fn main -> _/ebx: int { # represent trees in a 2D array of ints # wasteful since each tree is just one bit var trees-storage: (array int 0x2800) # 10k ints var trees/esi: (addr array int) <- address trees-storage var trees-length/ecx: int <- copy 0 var num-rows: int var width: int # phase 1: parse each row of trees from stdin { var line-storage: (stream byte 0x40) # 64 bytes 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-!= # wastefully recompute width on every line # zero error-checking; we assume input lines are all equally long copy-to width, 0 # turn each byte into a tree and append it $main:line-loop: { var done?/eax: boolean <- stream-empty? line compare done?, 0/false break-if-!= #? print-int32-decimal 0, num-rows #? print-string 0, " " #? print-int32-decimal 0, width #? print-string 0, "\n" var dest/ebx: (addr int) <- index trees, trees-length var c/eax: byte <- read-byte line # newline comes only at end of line compare c, 0xa/newline break-if-= # '#' = tree compare c, 0x23/hash { break-if-!= copy-to *dest, 1 } # anything else = no tree { break-if-= copy-to *dest, 0 } increment width trees-length <- increment loop } increment num-rows loop } } # phase 2: compute print-int32-decimal 0, num-rows print-string 0, "x" print-int32-decimal 0, width print-string 0, "\n" var row/ecx: int <- copy 0 var col/edx: int <- copy 0 var num-trees-hit/edi: int <- copy 0 { compare row, num-rows break-if->= var curr/eax: int <- index2d trees, row, col, width compare curr, 0 { break-if-= num-trees-hit <- increment } # right 3, down 1 col <- add 3 row <- add 1 loop } print-int32-decimal 0, num-trees-hit print-string 0, "\n" return 0 } fn index2d _arr: (addr array int), _row: int, _col: int, width: int -> _/eax: int { # handle repeating columns of trees var dummy/eax: int <- copy 0 var col/edx: int <- copy 0 dummy, col <- integer-divide _col, width # compute index var index/eax: int <- copy _row index <- multiply width index <- add col # look up array var arr/esi: (addr array int) <- copy _arr var src/eax: (addr int) <- index arr, index return *src }