Day 5

day_05/solve.nim

@@ -0,0 +1,75 @@
+import std/[strutils, sequtils, strformat, sugar]
+
+let input = readFile("day_05/input.txt")
+
+type Stacks = seq[seq[char]]
+
+proc readStacks(data: string): Stacks =
+  let lines = data.splitLines()
+  let count = lines[lines.len - 1].split("   ").len
+  var stacks = newSeqWith[char](count, newSeq[char]())
+  for line in 0..lines.len-2:
+    for stack in 0..count-1:
+      let crate = lines[line][stack*4..stack*4+2]
+      if not crate.isEmptyOrWhitespace:
+        stacks[stack].insert(lines[line][stack*4+1..stack*4+1])
+  return stacks
+
+#region debug-only
+proc echoStacks(stacks: Stacks) =
+  var height = stacks.mapIt(it.len).max()
+  while height > 0:
+    height -= 1
+    var line = ""
+    for i in 0..stacks.len-1:
+      if height < stacks[i].len:
+        # let item = stacks[i][height]
+        line.add fmt"[{stacks[i][height]}] "
+      else:
+        line.add fmt"    "
+    echo line
+  var line = ""
+  for i in 0..stacks.len-1:
+    line.add fmt" {i+1}  "
+  echo line
+#endregion debug-only
+
+proc moveCrate(stacks: var Stacks, operation: string, preserveOrder: bool = false) =
+  let tokens = operation.split(" ")
+  assert tokens[0] == "move"
+  let amount = tokens[1].parseInt
+  assert tokens[2] == "from"
+  let fromStack = tokens[3].parseInt - 1
+  assert tokens[4] == "to"
+  let toStack = tokens[5].parseInt - 1
+
+  if preserveOrder:
+    var moving = (0..amount-1).toSeq.mapIt(stacks[fromStack].pop)
+    for crate in 0..amount-1:
+      stacks[toStack].add(moving.pop)
+    return
+  
+  for i in 0..amount-1:
+    stacks[toStack].add(stacks[fromStack].pop)
+
+proc solvePart1() =
+  let inputData = input.split("\n\n")
+  var stacks = readStacks(inputData[0])
+  for operation in inputData[1].splitLines:
+    stacks.moveCrate(operation)
+  
+  stacks.echoStacks
+  echo stacks.mapIt(it[it.len - 1]).foldl(a & b, "")
+
+proc solvePart2() =
+  let inputData = input.split("\n\n")
+  var stacks = readStacks(inputData[0])
+  for operation in inputData[1].splitLines:
+    stacks.moveCrate(operation, true)
+  
+  stacks.echoStacks
+  echo stacks.mapIt(it[it.len - 1]).foldl(a & b, "")
+
+if isMainModule:
+  solvePart1()
+  solvePart2()