Day 3

2020/src/day3.nim

@@ -1,9 +1,23 @@
 import streams
 
-let sledSlope = (3, 1)
+proc sled(s: Stream, velx: int, vely: int): int =
+  setPosition(s, 0)
+  result = 0
+  var xpos = 0
+  var ypos = 0
+  for line in s.lines():
+    ypos += 1
+    if (ypos - 1) mod vely > 0:
+      continue
+    if line[xpos mod line.len()] == '#':
+      result += 1
+    xpos += velx
 
 proc part1*(s: Stream): int =
-  0
+  sled(s, 3, 1)
 
 proc part2*(s: Stream): int =
-  0
+  result = part1(s)
+  for vels in [(1, 1), (5, 1), (7, 1), (1, 2)]:
+    let (velx, vely) = vels
+    result *= sled(s, velx, vely)

2020/src/day_loader.nim

@@ -7,6 +7,7 @@ macro loadDays(): untyped =
     let module = fmt"day{day}"
     if fileExists joinPath("src/", &"{module}.nim"):
       result.add parseStmt fmt"from {module} import nil"
+      # TODO: do I "need" to close these streams?
       solver_str = solver_str & &"""
       {day}: proc(): tuple[part1: int, part2: int] =
         echo "Day {day}"