How is 304099 output its input and halt

# advent-of-code

[asad.awadia]

How is 304099 output its input and halt

[mickeelm]

1. Reads 3 which is input, takes the input and stores it in the given position per the first parameter which is 0. So position 0 now has the input value.
2. Moves two positions, reads 4 which is output. Checks the given position per the first parameter which is 0, where the input value is stored
3. moves two position. 99 - halt

[mickeelm]

The effect being that what your input is, will be the program's output before it halts

[asad.awadia]

But what is the input value?

[asad.awadia]

What gets stored in position 0

[mickeelm]

You provide this

[asad.awadia]

....

[mickeelm]

For example as an argument to a function

[asad.awadia]

I might just skip today’s one

[mickeelm]

Think of it as a variable

[mickeelm]

For part 1, the input will be "1" (well, the number 1)

[mickeelm]

so if you just have val input = 1 somewhere you'll be fine

[mickeelm]

so 304099 would be 104099 when processed

[mickeelm]

and have made the output 1

[mickeelm]

And the "output"...you can print that if you wish, I just stored my outputs in a list. The interesting part today is the last output, so that's all you need. I just wanted to make sure all my other output values were 0.

[mickeelm]

Do you understand?

[mickeelm]

Like, the input value could be anything, but per part one's instructions, it must be 1. Only one input value is needed, he calls it an "input instruction" and it's just a way of telling our "intcode computer how to run", but in practice it means nothing, it's just a story.

For part 1, you can read the instruction "Opcode 3 takes a single integer as input and saves it to the position given by its only parameter." as

"Opcode 3 - set the value 1 at the position given by it's only parameter"

[mickeelm]

Hope that helps - time to sleep in my part of the world 🙂