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--- Day 5: Sunny with a Chance of Asteroids ---
You're starting to sweat as the ship makes its way toward Mercury. The Elves suggest that you get
the air conditioner working by upgrading your ship computer to support the Thermal Environment
Supervision Terminal.
The Thermal Environment Supervision Terminal (TEST) starts by running a [1m[97mdiagnostic program[0m (your
puzzle input). The TEST diagnostic program will run on your existing Intcode computer after a few
modifications:
[1m[97mFirst[0m, you'll need to add [1m[97mtwo new instructions[0m:
- Opcode 3 takes a single integer as [1m[97minput[0m and saves it to the position given by its only
parameter. For example, the instruction 3,50 would take an input value and store it at address 50.
- Opcode 4 [1m[97moutputs[0m the value of its only parameter. For example, the instruction 4,50 would output
the value at address 50.
Programs that use these instructions will come with documentation that explains what should be
connected to the input and output. The program 3,0,4,0,99 outputs whatever it gets as input, then
halts.
[1m[97mSecond[0m, you'll need to add support for [1m[97mparameter modes[0m:
Each parameter of an instruction is handled based on its parameter mode. Right now, your ship
computer already understands parameter mode 0, [1m[97mposition mode[0m, which causes the parameter to be
interpreted as a [1m[97mposition[0m - if the parameter is 50, its value is [1m[97mthe value stored at address 50 in
memory[0m. Until now, all parameters have been in position mode.
Now, your ship computer will also need to handle parameters in mode 1, [1m[97mimmediate mode[0m. In immediate
mode, a parameter is interpreted as a [1m[97mvalue[0m - if the parameter is 50, its value is simply
[1m[97m50[0m.
Parameter modes are stored in the same value as the instruction's opcode. The opcode is a two-digit
number based only on the ones and tens digit of the value, that is, the opcode is the rightmost two
digits of the first value in an instruction. Parameter modes are single digits, one per parameter,
read right-to-left from the opcode: the first parameter's mode is in the hundreds digit, the second
parameter's mode is in the thousands digit, the third parameter's mode is in the ten-thousands
digit, and so on. Any missing modes are 0.
For example, consider the program 1002,4,3,4,33.
The first instruction, 1002,4,3,4, is a [1m[97mmultiply[0m instruction - the rightmost two digits of the first
value, 02, indicate opcode 2, multiplication. Then, going right to left, the parameter modes are 0
(hundreds digit), 1 (thousands digit), and 0 (ten-thousands digit, not present and therefore zero):
ABCDE
1002
DE - two-digit opcode, 02 == opcode 2
C - mode of 1st parameter, 0 == position mode
B - mode of 2nd parameter, 1 == immediate mode
A - mode of 3rd parameter, 0 == position mode,
omitted due to being a leading zero
This instruction multiplies its first two parameters. The first parameter, 4 in position mode,
works like it did before - its value is the value stored at address 4 (33). The second parameter, 3
in immediate mode, simply has value 3. The result of this operation, 33 * 3 = 99, is written
according to the third parameter, 4 in position mode, which also works like it did before - 99 is
written to address 4.
Parameters that an instruction writes to will [1m[97mnever be in immediate mode[0m.
[1m[97mFinally[0m, some notes:
- It is important to remember that the instruction pointer should increase by [1m[97mthe number of values
in the instruction[0m after the instruction finishes. Because of the new instructions, this amount is
no longer always 4.
- Integers can be negative: 1101,100,-1,4,0 is a valid program (find 100 + -1, store the result in
position 4).
The TEST diagnostic program will start by requesting from the user the ID of the system to test by
running an [1m[97minput[0m instruction - provide it 1, the ID for the ship's air conditioner unit.
It will then perform a series of diagnostic tests confirming that various parts of the Intcode
computer, like parameter modes, function correctly. For each test, it will run an
[1m[97moutput[0m instruction indicating how far the result of the test was from the expected value, where 0
means the test was successful. Non-zero outputs mean that a function is not working correctly;
check the instructions that were run before the output instruction to see which one failed.
Finally, the program will output a [1m[97mdiagnostic code[0m and immediately halt. This final output isn't an
error; an output followed immediately by a halt means the program finished. If all outputs were
zero except the diagnostic code, the diagnostic program ran successfully.
After providing 1 to the only input instruction and passing all the tests, [1m[97mwhat diagnostic code does
the program produce?[0m
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