68 lines
1.4 KiB
Lua
68 lines
1.4 KiB
Lua
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-- see if the file exists
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local function file_exists(file)
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local f = io.open(file, "rb")
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if f then
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f:close()
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end
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return f ~= nil
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end
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-- get all lines from a file, returns an empty
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-- list/table if the file does not exist
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local function lines_from(file)
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if not file_exists(file) then
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return {}
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end
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local lines = {}
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for line in io.lines(file) do
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lines[#lines + 1] = line
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end
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return lines
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end
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-- tests the functions above
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local file = "input"
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local lines = lines_from(file)
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local input = ""
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for _, line in pairs(lines) do
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input = input .. line
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end
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local instructions = {}
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-- print all line numbers and their contents
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for pos, a, b in string.gmatch(input, "()mul%((%d+),(%d+)%)") do
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---@diagnostic disable-next-line: redefined-local
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local a, b = tonumber(a), tonumber(b)
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local product = a * b
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instructions[#instructions + 1] = {
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pos = pos,
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product = product,
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}
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end
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for pos in string.gmatch(input, "()do%(%)") do
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instructions[#instructions + 1] = { pos = pos, enable = true }
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end
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for pos in string.gmatch(input, "()don't%(%)") do
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instructions[#instructions + 1] = { pos = pos, enable = false }
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end
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table.sort(instructions, function(a, b)
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return a.pos < b.pos
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end)
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local total = 0
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local enabled = true
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for _, instruction in ipairs(instructions) do
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if instruction.enable ~= nil then
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enabled = instruction.enable
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elseif enabled then
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total = total + instruction.product
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end
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end
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io.output():write(total)
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