2022/09/both.nim

@@ -0,0 +1,49 @@
+import
+  std/strformat,
+  std/strutils
+
+import
+  ../../adventofcode
+
+type
+  Position = tuple[x, y: int]
+
+let input = adventofcode.getInput()
+
+var knots: seq[Position] = @[]
+const knotCount =
+  when not defined(second): 2
+  else: 10
+for i in 0 ..< knotCount:
+  knots.add (0, 0)
+
+var visitedByLastKnot: seq[Position] = @[(0, 0)]
+
+for line in input.splitLines():
+  let direction = line[0]
+  let moves = parseInt line[2 .. ^1]
+  for i in 0 ..< moves:
+    case direction
+    of 'L': knots[0].x -= 1
+    of 'R': knots[0].x += 1
+    of 'U': knots[0].y -= 1
+    of 'D': knots[0].y += 1
+    else: discard
+
+    for i in 1 ..< len knots:
+      let dx = knots[i - 1].x - knots[i].x
+      let dy = knots[i - 1].y - knots[i].y
+      let tension = abs(dx) > 1 or abs(dy) > 1
+      if tension:
+        if abs(dx) > 0:
+          let moveKnotX = if dx > 0: 1 else: -1
+          knots[i].x += moveKnotX
+        if abs(dy) > 0:
+          let moveKnotY = if dy > 0: 1 else: -1
+          knots[i].y += moveKnotY
+
+        if i == high knots:
+          if knots[i] notin visitedByLastKnot:
+            visitedByLastKnot.add knots[i]
+
+echo fmt"Answer: {len visitedByLastKnot}"

2022/09/prev-first.nim

@@ -0,0 +1,36 @@
+import
+  std/strformat,
+  std/strutils
+
+import
+  ../../adventofcode
+
+type
+  Position = tuple[x, y: int]
+
+let input = adventofcode.getInput()
+
+var lastHead: Position = (0, 0)
+var head: Position = (0, 0)
+var tail: Position = (0, 0)
+var visited: seq[Position] = @[(0, 0)]
+
+for line in input.splitLines():
+  let direction = line[0]
+  let moves = parseInt line[2 .. ^1]
+  for i in 0 ..< moves:
+    lastHead = head
+    case direction
+    of 'L': head.x -= 1
+    of 'R': head.x += 1
+    of 'U': head.y -= 1
+    of 'D': head.y += 1
+    else: discard
+
+    var tension = abs(head.x - tail.x) > 1 or abs(head.y - tail.y) > 1
+    if tension:
+      tail = lastHead
+      if tail notin visited:
+        visited.add tail
+
+echo fmt"Answer: {len visited}"