about summary refs log tree commit diff stats
path: root/apps/advent2020/3b.mu
blob: fcc9261a77b2c23fdfff65c43247d2a6b0a39f78 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
# 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
  var product/edi: int <- copy 1
  var result/eax: int <- num-trees-hit trees, width, num-rows, 1, 1
  print-int32-decimal 0, result
  print-string 0, " x "
  product <- multiply result
  var result/eax: int <- num-trees-hit trees, width, num-rows, 3, 1
  print-int32-decimal 0, result
  print-string 0, " x "
  product <- multiply result
  var result/eax: int <- num-trees-hit trees, width, num-rows, 5, 1
  print-int32-decimal 0, result
  print-string 0, " x "
  product <- multiply result
  var result/eax: int <- num-trees-hit trees, width, num-rows, 7, 1
  print-int32-decimal 0, result
  print-string 0, " x "
  product <- multiply result
  var result/eax: int <- num-trees-hit trees, width, num-rows, 1, 2
  print-int32-decimal 0, result
  print-string 0, " = "
  product <- multiply result
  print-int32-hex 0, product
  print-string 0, "\n"
  return 0
}

fn num-trees-hit trees: (addr array int), width: int, num-rows: int, right: int, down: int -> _/eax: int {
#?   print-string 0, "== "
#?   print-int32-decimal 0, right
#?   print-string 0, " "
#?   print-int32-decimal 0, down
#?   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->=
#?     print-int32-decimal 0, col
#?     print-string 0, "\n"
    var curr/eax: int <- index2d trees, row, col, width
    compare curr, 0
    {
      break-if-=
      num-trees-hit <- increment
    }
    col <- add right
    row <- add down
    loop
  }
  return num-trees-hit
}

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
#?   print-string 0, "  "
#?   print-int32-decimal 0, col
#?   print-string 0, "\n"
  # 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
}