aoc/day1/day1.lua

--Lua 5.4.2
local File = io.open("input.txt", "r")

if not File then
    print("File not found")
    return
end

local LeftList = {}
local RightList = {}
local Distances = {}

for Line in File:lines() do
    local LeftId, RightId = Line:match("(%d+)%s+(%d+)")
    table.insert(LeftList, tonumber(LeftId))
    table.insert(RightList, tonumber(RightId))
end

File:close()

local function SortFunction(a, b)
    return a < b
end

table.sort(LeftList, SortFunction)
table.sort(RightList, SortFunction)

if #LeftList ~= #RightList then
    print("Lists are not the same size")
    return
end

for ListIndex = 1, #LeftList do
    local LeftId, RightId = LeftList[ListIndex], RightList[ListIndex]
    local Distance = math.abs(LeftId - RightId)
    Distances[ListIndex] = Distance
end

local TotalDistance = 0
for _, Distance in next, Distances do
    TotalDistance = TotalDistance + Distance
end

print("Total distance:", TotalDistance)