.gitignore

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+# input files
+input.txt

2021/1/first.nim

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+import
+  ../../adventofcode,
+  sequtils,
+  strformat,
+  strutils
+
+let input = adventofcode.getInput(2021, 1)
+let lines = input.splitLines()[0 .. ^2].mapIt(it.parseInt())
+
+var depths = 0
+var prevResult = lines[0]
+
+for line in lines[1 .. ^1]:
+  let currResult = line
+  if prevResult < currResult:
+    depths += 1
+
+  prevResult = currResult
+  
+echo fmt"Answer: {depths}"

2021/1/second.nim

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+import
+  ../../adventofcode,
+  sequtils,
+  strformat,
+  strutils
+
+let input = adventofcode.getInput(2021, 1)
+let lines = input.splitLines()[0 .. ^2].mapIt(it.parseInt())
+
+var depths = 0
+var prevSum = lines[0] + lines[1] + lines[2]
+
+for idx in 0 .. lines.high():
+  if idx + 2 > lines.high(): break
+
+  let currSum = lines[idx] + lines[idx + 1] + lines[idx + 2]
+  if prevSum < currSum:
+    depths += 1
+
+  prevSum = currSum
+  
+echo fmt"Answer: {depths}"

2021/2/first.nim

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+import
+  ../../adventofcode,
+  strutils,
+  strformat
+
+let input = adventofcode.getInput(2021, 2)
+let lines = input.splitLines()[0 .. ^2]
+
+var horizontalPosition = 0
+var depth = 0
+
+for line in lines:
+  var command = line.split(" ")
+  case command[0]:
+    of "forward":
+      horizontalPosition += command[1].parseInt()
+    of "up":
+      depth -= command[1].parseInt()
+    of "down":
+      depth += command[1].parseInt()
+
+echo fmt"Answer: {horizontalPosition * depth}"

2021/2/second.nim

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+import
+  ../../adventofcode,
+  strutils,
+  strformat
+
+let input = adventofcode.getInput(2021, 2)
+let lines = input.splitLines()[0 .. ^2]
+
+var horizontalPosition = 0
+var depth = 0
+var aim = 0
+
+for line in lines:
+  var command = line.split(" ")
+  case command[0]:
+    of "forward":
+      horizontalPosition += command[1].parseInt()
+      depth += aim * command[1].parseInt()
+    of "up":
+      aim -= command[1].parseInt()
+    of "down":
+      aim += command[1].parseInt()
+
+echo fmt"Answer: {horizontalPosition * depth}"

2021/3/first.nim

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+import
+  ../../adventofcode,
+  sequtils,
+  strutils,
+  strformat
+
+let input = adventofcode.getInput(2021, 3)
+let lines = input.splitLines()[0 .. ^2]
+
+var gammaRateBinary = ""
+var epsilonRateBinary = ""
+
+for idx in 0 .. lines[0].high():
+  let a = lines.countIt(it[idx] == '0')
+  let b = lines.countIt(it[idx] == '1')
+  if a > b:
+    gammaRateBinary.add '0'
+    epsilonRateBinary.add '1'
+  else:
+    gammaRateBinary.add '1'
+    epsilonRateBinary.add '0'
+    
+let gammaRate = gammaRateBinary.parseBinInt()
+let epsilonRate = epsilonRateBinary.parseBinInt()
+
+echo fmt"Answer: {gammaRate * epsilonRate}"

2021/3/second.nim

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+import
+  ../../adventofcode,
+  sequtils,
+  strutils,
+  strformat
+
+let input = adventofcode.getInput(2021, 3)
+let lines = input.splitLines()[0 .. ^2]
+
+var oxygenGenRateValues = lines
+var co2ScrubberRateValues = lines
+
+while oxygenGenRateValues.len() > 1:
+  for idx in 0 .. oxygenGenRateValues[0].high():
+    let a = oxygenGenRateValues.countIt(it[idx] == '0')
+    let b = oxygenGenRateValues.countIt(it[idx] == '1')
+    if a == b or a < b:
+      oxygenGenRateValues = oxygenGenRateValues.filterIt(it[idx] == '1')
+    else:
+      oxygenGenRateValues = oxygenGenRateValues.filterIt(it[idx] == '0')
+
+    if oxygenGenRateValues.len() == 1: break
+    
+while co2ScrubberRateValues.len() > 1:
+  for idx in 0 .. co2ScrubberRateValues[0].high():
+    let a = co2ScrubberRateValues.countIt(it[idx] == '0')
+    let b = co2ScrubberRateValues.countIt(it[idx] == '1')
+    if a == b or a < b:
+      co2ScrubberRateValues = co2ScrubberRateValues.filterIt(it[idx] == '0')
+    else:
+      co2ScrubberRateValues = co2ScrubberRateValues.filterIt(it[idx] == '1')
+      
+    if co2ScrubberRateValues.len() == 1: break
+
+let o2GenRate = oxygenGenRateValues[0].parseBinInt()
+let co2ScrubberRate = co2ScrubberRateValues[0].parseBinInt()
+
+echo fmt"Answer: {o2GenRate * co2ScrubberRate}"

2021/4/first.nim

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+import
+  ../../adventofcode,
+  math,
+  sequtils,
+  strutils,
+  strformat
+  
+import
+  x/board
+  
+let input = adventofcode.getInput(2021, 4)
+let lines = input.splitLines()[0 .. ^2]
+
+let drawn = lines[0].split(",").mapIt(it.parseInt())
+var currentlyDrawn: seq[int] = @[]
+var boards: seq[Board] = @[]
+
+# Determinate boards from our input
+var currBoard = newBoard()
+for line in lines[2 .. ^1]:
+  if line.len() != 0:
+    currBoard.grid.add line.split(" ").filterIt(it.len() > 0).mapIt(it.parseInt())
+    
+  else:
+    boards.add currBoard
+    currBoard = newBoard()
+    
+var determinatedWinner = false
+var winningBoard: Board
+while not determinatedWinner:
+  if currentlyDrawn.len() == drawn.len():
+    # We run out of numbers to draw
+    break
+
+  let next = drawn[currentlyDrawn.len()]
+  currentlyDrawn.add next
+  
+  for board in boards:
+    board.markNumber next
+    
+    if board.winning:
+      winningBoard = board
+      determinatedWinner = true
+      break
+
+echo $winningBoard
+let winningBoardScore = currentlyDrawn[^1] * math.sum winningBoard.getUnmarkedNumbers()
+
+echo fmt"Boards: {boards.len()}"
+echo fmt"Answer: {winningBoardScore}"

2021/4/x/board.nim

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+import
+  sequtils,
+  strutils
+
+type
+  Board* = ref object
+    grid*: seq[seq[int]]
+    marks*: seq[seq[bool]]
+    
+proc newBoard*(): Board =
+  result = Board(
+    marks: @[
+      @[false, false, false, false, false],
+      @[false, false, false, false, false],
+      @[false, false, false, false, false],
+      @[false, false, false, false, false],
+      @[false, false, false, false, false]
+    ]
+  )
+  
+proc `$`*(this: Board): string = this.grid.mapIt(it.mapIt($it).join(" ")).join("\n")
+  
+proc winning*(this: Board): bool =
+  for i in 0 .. 4:
+    if this.marks.allIt(it[i] == true):
+      return true
+    if this.marks[i].allIt(it == true):
+      return true
+
+proc markNumber*(this: Board, number: int) =
+  for i in 0 .. 4:
+    for j in 0 .. 4:
+      if this.grid[i][j] == number:
+        this.marks[i][j] = true
+    
+proc getUnmarkedNumbers*(this: Board): seq[int] =
+  for i in 0 .. 4:
+    for j in 0 .. 4:
+      if this.marks[i][j] == false:
+        result.add this.grid[i][j]

adventofcode.nim

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+import
+  httpclient,
+  os,
+  strformat
+  
+let session = os.getEnv("SESSION")
+if session == "":
+  echo "Missing SESSION environment variable."
+  quit 1
+
+proc getInput*(year, day: int): string =
+  try:
+    let input = readFile(getCurrentDir() / "input.txt")
+    
+    return input
+  except IOError:
+    let client = newHttpClient()
+    client.headers = newHttpHeaders({ "Cookie": fmt"session={session}" })
+
+    let input = client.getContent fmt"https://adventofcode.com/{year}/day/{day}/input"
+    
+    writeFile(getCurrentDir() / "input.txt", input)
+    
+    return input