Added solution for Puzzle 14 in Lua

Author: janschaefer

14/main.lua

@@ -0,0 +1,202 @@
+function parseInput(filePath)
+  local file = io.open(filePath, "r")  -- Open file for reading
+  if not file then return nil end      -- Return nil if file can't be opened
+
+  local array2D = {}
+  for line in file:lines() do
+      local row = {}
+      for char in line:gmatch(".") do   -- Iterate over each character in the line
+          table.insert(row, char)       -- Insert character into the row
+      end
+      table.insert(array2D, row)        -- Insert row into the 2D array
+  end
+
+  file:close()                          -- Close the file
+  return array2D
+end
+
+function copyRoundedRockPositions(roundedRocks)
+  local newArray = {}
+  for i, value in ipairs(roundedRocks) do
+      newArray[i] = {row = value.row, column = value.column }
+  end
+  return newArray
+end
+
+function positionsAreEqual(roundedRocks1, roundedRocks2)
+  for i = 1, #roundedRocks1 do
+      if roundedRocks1[i].row ~= roundedRocks2[i].row then
+          return false
+      end
+      if roundedRocks1[i].column ~= roundedRocks2[i].column then
+          return false
+      end
+  end
+  return true
+end
+
+function findRockPositions(history, roundedRocks) 
+  for i = 1, #history do
+    if positionsAreEqual(history[i], roundedRocks) then
+      return i
+    end
+  end
+  return -1
+end
+
+function findRoundedRocks(array2D)
+  local positions = {}
+  for rowIndex, row in ipairs(array2D) do
+      for columnIndex, char in ipairs(row) do
+          if char == 'O' then
+              table.insert(positions, {row = rowIndex, column = columnIndex})
+          end
+      end
+  end
+  return positions
+end
+
+local function sortByRowDesc(a, b) 
+  if (a.row == b.row) then
+    return a.column > b.column
+  end
+  return a.row > b.row;
+end
+
+local function sortByRowAsc(a, b) 
+  if (a.row == b.row) then
+    return a.column < b.column
+  end
+  return a.row < b.row;
+end
+
+local function sortByColDesc(a, b) 
+  if (a.column == b.column) then
+    return a.row > b.row
+  end
+  return a.column > b.column;
+end
+
+local function sortByColAsc(a, b) 
+  if (a.column == b.column) then
+    return a.row < b.row
+  end
+  return a.column < b.column;
+end
+
+
+function tiltNorth(array2D, roundedRocks)
+  table.sort(roundedRocks, sortByRowAsc)
+  for _, pos in ipairs(roundedRocks) do
+      while pos.row > 1 and array2D[pos.row - 1][pos.column] == '.' do
+        array2D[pos.row][pos.column] = '.'
+        pos.row = pos.row - 1
+        array2D[pos.row][pos.column] = 'O'
+      end
+  end
+end
+
+function tiltSouth(array2D, roundedRocks)
+  table.sort(roundedRocks, sortByRowDesc)
+  for _, pos in ipairs(roundedRocks) do
+      while pos.row < #array2D and array2D[pos.row + 1][pos.column] == '.' do
+        array2D[pos.row][pos.column] = '.'
+        pos.row = pos.row + 1
+        array2D[pos.row][pos.column] = 'O'
+      end
+  end
+end
+
+function tiltEast(array2D, roundedRocks)
+  table.sort(roundedRocks, sortByColDesc)
+  for _, pos in ipairs(roundedRocks) do
+      while pos.column < #array2D and array2D[pos.row][pos.column + 1] == '.' do
+        array2D[pos.row][pos.column] = '.'
+        pos.column = pos.column + 1
+        array2D[pos.row][pos.column] = 'O'
+      end
+  end
+end
+
+function tiltWest(array2D, roundedRocks)
+  table.sort(roundedRocks, sortByColAsc)
+  for _, pos in ipairs(roundedRocks) do
+      while pos.column > 1 and array2D[pos.row][pos.column - 1] == '.' do
+        array2D[pos.row][pos.column] = '.'
+        pos.column = pos.column - 1
+        array2D[pos.row][pos.column] = 'O'
+      end
+  end
+end
+
+function cycle(charArray2D, roundedRocks)
+  tiltNorth(charArray2D, roundedRocks)
+  tiltWest(charArray2D, roundedRocks)
+  tiltSouth(charArray2D, roundedRocks)
+  tiltEast(charArray2D, roundedRocks)
+end
+
+
+function calculateWeight(array2D, roundedRocks)
+  local totalWeight = 0
+  for _, pos in ipairs(roundedRocks) do
+    local weight = (#array2D - pos.row) + 1
+    totalWeight = totalWeight + weight
+  end
+  return totalWeight
+end
+
+function printArray(array2D)
+  for i, row in ipairs(array2D) do
+      for j, char in ipairs(row) do
+          io.write(char)
+      end
+      io.write("\n")
+  end
+  io.write("\n")
+  
+end
+
+function solve(pathToFile)
+  local charArray2D = parseInput(pathToFile)
+  local roundedRocks = findRoundedRocks(charArray2D)
+  tiltNorth(charArray2D, roundedRocks)
+  io.write(calculateWeight(charArray2D, roundedRocks))
+  io.write("\n")
+end
+
+function solve2(pathToFile)
+  local charArray2D = parseInput(pathToFile)
+  local roundedRocks = findRoundedRocks(charArray2D)
+  
+  local historyOfPos = { }
+  
+  local countUntilRepeats;
+  local cycleLength
+  for i = 1, 1000000000 do
+    cycle(charArray2D, roundedRocks)
+  
+    local existingPos = findRockPositions(historyOfPos, roundedRocks)
+    if existingPos > -1 then
+      countUntilRepeats = existingPos
+      cycleLength = i - countUntilRepeats
+      break
+    end
+  
+    table.insert(historyOfPos, copyRoundedRockPositions(roundedRocks))
+  end
+  
+  local remainingCycles = (1000000000 - countUntilRepeats) % cycleLength
+  
+  for i = 1, remainingCycles do
+    cycle(charArray2D, roundedRocks)
+  end
+  
+  
+  io.write(calculateWeight(charArray2D, roundedRocks))
+  io.write("\n")
+end
+
+local pathToFile = "input"
+solve(pathToFile)
+solve2(pathToFile)