Day 9

2 files changed, 69 insertions, 8 deletions

diff --git a/day9/example.txt b/day9/example.txt
index 9874df2..60bd43b 100644
--- a/day9/example.txt
+++ b/day9/example.txt
@@ -1,8 +1,8 @@
-R 4
-U 4
-L 3
-D 1
-R 4
-D 1
-L 5
-R 2
+R 5
+U 8
+L 8
+D 3
+R 17
+D 10
+L 25
+U 20
diff --git a/day9/solution.nim b/day9/solution.nim
index e69de29..ef25492 100644
--- a/day9/solution.nim
+++ b/day9/solution.nim
@@ -0,0 +1,61 @@
+import strutils
+import sequtils
+import sets
+
+type Move = tuple[Direction: char, Distance: int]
+type Position = tuple[r: int, c: int]
+
+proc parse(content: seq[string]): seq[Move] =
+  let moves = map(content, 
+                  proc (line: string): Move =
+                    let temp = line.split(" ")
+                    (temp[0][0], temp[1].parseInt())
+              )
+  return moves
+
+proc move(rope: var seq[Position], uniqPositions: var HashSet[Position]): void =
+  for i in 1 ..< rope.len():
+    # rope[i-1] = leader
+    # rope[i] = follower
+    let roffset = rope[i-1].r - rope[i].r
+    let coffset = rope[i-1].c - rope[i].c
+
+    if roffset in [2, -2]:
+      rope[i].r += int(roffset/2)
+      if coffset in [-1, 1]:
+        rope[i].c = rope[i-1].c
+
+    if coffset in [2, -2]:
+      rope[i].c += int(coffset/2)
+      if roffset in [-1, 1]:
+        rope[i].r = rope[i-1].r
+
+  uniqPositions.incl(rope[rope.len()-1])
+
+proc emulate(moves: seq[Move], len = 2): int =
+  var rope = newSeq[Position](len)
+  var uniqPositions: HashSet[Position]
+  init(uniqPositions)
+  echo rope
+  for move in moves:
+    for i in 1 .. move.Distance:
+      case move.Direction:
+        of 'U':
+          rope[0].r -= 1
+        of 'R':
+          rope[0].c += 1
+        of 'D':
+          rope[0].r += 1
+        of 'L':
+          rope[0].c -= 1
+        else:
+          assert(false)
+      move(rope, uniqPositions)
+
+  return len(uniqPositions)
+
+let content = readFile("./input.txt").strip().splitLines()
+let moves = parse(content)
+
+echo emulate(moves)
+echo emulate(moves, 10)