1 files changed, 70 insertions, 0 deletions

diff --git a/day10/solution.nim b/day10/solution.nim
new file mode 100644
index 0000000..4277696
--- /dev/null
+++ b/day10/solution.nim
@@ -0,0 +1,70 @@
+import strutils
+import sequtils
+import sugar
+
+type
+  Instruction = tuple
+    opcode: string
+    arg: int
+
+  Program = seq[Instruction]
+
+func instructionFromString(str: string): Instruction =
+  let tokens = str.split()
+  let opcode = tokens[0]
+  var arg: int
+  if tokens.len() > 1:
+    arg = tokens[1].parseInt()
+  else:
+    arg = 0
+  
+  (opcode, arg)
+
+func parseProgram(content: seq[string]): Program =
+  result = map(
+    content,
+    (line) => instructionFromString(line)
+  )
+
+proc checkSignal(cycle: int, x: int): int =
+  # cycle+1 because cycle is supposed to be starting at 0
+  if cycle+1 in [20, 60, 100, 140, 180, 220]:
+    result = x * (cycle+1)
+
+var CRT: array[0 .. 5, array[0 .. 39, char]]
+proc draw(cycle: int, x: int): void =
+  let
+    col = cycle mod 40
+    row = cycle div 40
+  if col in [x-1, x, x+1]:
+    CRT[row][col] = '#'
+
+proc execute(program: Program): int =
+  var
+    x = 1
+    cycle = 0
+
+  for i, instr in program:
+    result += checkSignal(cycle, x)
+    draw(cycle, x)
+    case instr.opcode:
+      of "addx":
+        result += checkSignal(cycle+1, x)
+        draw(cycle+1, x)
+        x += instr.arg
+        cycle += 2
+      of "noop":
+        cycle += 1
+      else:
+        assert(false)
+
+let content = readFile("./input.txt").strip().splitLines()
+let program = parseProgram(content)
+
+for row in 0 ..< 6:
+  for col in 0 ..< 40: 
+    CRT[row][col] = ' '
+
+echo execute(program)
+for row in CRT:
+  echo row.join()