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69 lines
1.7 KiB
69 lines
1.7 KiB
5 years ago
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function check_mem(max, offs)
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if max < offs then
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print(string.format("Error: Memory offset out of bounds: %d", offs))
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os.exit(false)
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end
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end
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function interpret(mem)
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pos = 1
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while true do
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if #mem < pos then
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print(string.format("Instruction pointer ran off of memory"))
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os.exit(false)
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end
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if mem[pos] == 1 or mem[pos] == 2 then
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if #mem < pos + 3 then
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print(string.format("Error: Opcode too short at end of memory: %d", pos))
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os.exit(false)
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end
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arg1 = mem[pos + 1] + 1
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arg2 = mem[pos + 2] + 1
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res = mem[pos + 3] + 1
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check_mem(#mem, arg1)
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check_mem(#mem, arg2)
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check_mem(#mem, res)
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if mem[pos] == 1 then
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mem[res] = mem[arg1] + mem[arg2]
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else
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mem[res] = mem[arg1] * mem[arg2]
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end
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pos = pos + 4
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elseif mem[pos] == 99 then
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return
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else
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print(string.format("Error: Invalid opcode %d at %d", mem[pos], pos - 1))
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os.exit(false)
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end
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end
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end
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file = io.open(arg[1])
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memory = {}
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for num in string.gmatch(file:read(), "(%d+),") do
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table.insert(memory, tonumber(num))
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end
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file:close()
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memory_p1 = {table.unpack(memory)}
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memory_p1[2] = 12
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memory_p1[3] = 2
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interpret(memory_p1)
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print("Part 1:", memory_p1[1])
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-- Brute force
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for noun = 0, 99 do
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for verb = 0, 99 do
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memory_p2 = {table.unpack(memory)}
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memory_p2[2] = noun
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memory_p2[3] = verb
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interpret(memory_p2)
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if memory_p2[1] == 19690720 then
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print("Part 2:", 100 * noun + verb)
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os.exit(true)
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end
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end
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end
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