AdventOfCode-js-2019

AdventOfCode-js-2019

Advent of Code 2019 solutions done in NodeJS

Explanation

A big theme of this year's challenge is an Intcode Computer the user is tasked with designing. This computer works on programs from a tape, or stack, of integers. Some of these integers on the stack are instructions, or opcodes. Opcodes are 2-digit integers (assumed 0 prefixed) that represent actions for the computer to perform on the stack. All integers on the stack are represented as decimal numbers.

Parameter Modes

The Intcode Computer being built has two Parameter Modes: Position Mode, and Immediate Mode. Each opcode can self-describe the Parameter Mode to use for each of its parameters independent of each other.

Position Mode

In Position Mode, the computer's default setting, parameters passed to functions are considered to be addresses where the actual value to operate on can be found. Thus, in Position Mode, an input of 42 tells the computer to look at memory address 42 on the stack.

Immediate Mode

In Immediate Mode, the parameter is taken "as is", and operated on accordingly. For example, 42 in Immediate Mode is treated as 42.

Relative Mode

Relative mode acts similarly to Position Mode, where the final value is retrieved from another location in memory. It's different, though, in that a "Relative Base Offset" is added to that memory address to get the true address. The Relative Base Offset value is tracked by the computer's memory stack.

Opcode Dictionary

• 01 - ADD
• 02 - MULTIPLY
• 03 - INPUT
• 04 - OUTPUT
• 05 - JUMP IF TRUE
• 06 - JUMP IF FALSE
• 07 - LESS THAN
• 08 - EQUALS
• 09 - MODIFY RELATIVE BASE
• 99 - HALT

01 - ADD

Add two numbers, and outputs to the memory address in the third parameter. Opcode accepts 2 Postion Mode markers.

Forms	Description
1	Add two values in Position Mode
01	Add two values in Position Mode
101	Add two values. First in Immediate Mode, second in Position Mode
001	Add two values in Position Mode
1001	Add two values. First in Position Mode, second in Immediate Mode
1101	Add two values in Position Mode

Parameters	Description
Operand 1	First number, or address of the number, to add
Operand 2	Second number, or address of the number, to add
Output position	The memory address to store the result in

02 - MULTIPLY

Multiply two numbers, and outputs to the memory address in the third parameter. Opcode accepts 2 Postion Mode markers.

Forms	Description
2	Multiply two values in Position Mode
02	Multiply two values in Position Mode
102	Multiply two values. First in Immediate Mode, second in Position Mode
002	Multiply two values in Position Mode
1002	Multiply two values. First in Position Mode, second in Immediate Mode
1102	Multiply two values in Position Mode

Parameters	Description
Operand 1	First number, or address of the number, to multiply
Operand 2	Second number, or address of the number, to multiply
Output position	The memory address to store the result in

03 - INPUT

Takes input from either the runtime input array, or from the console, depending on the Input Mode Map. The Input Mode Map is an array of value, either INPUT_FROM_CONSOLE or INPUT_FROM_RUNTIME_STACK, provided to the computer before running. Each time an INPUT opcode is encounter, an Input Mode is shifted off of this array. Once the array is empty, any further INPUT opcodes encounter will assume INPUT_FROM_RUNTIME_STACK unless the inputFromConsole option is true.

If the input is set to come from the runtime input array, and the array is empty, the computer will pause execution until either the Run function for the Input functions are called on the computer.

The output position may be in either Immediate Mode or Relative Mode.

Forms	Description
3	Receive input
03	Receive input
103	Receive input in Immediate Mode
203	Receive input in Relative Mode

Parameters	Description
Output position	The memory address to store the result in

04 - OUTPUT

Outputs either a value from a memory address, or a literal value. This output is initially sent to an outputValues array. If the computer's outputToConsole option is true, then the output is instead displayed in the console.

If the computer has an outputComputer set, then the output is instead sent to the output computer through an Input call to that computer.

Forms	Description
4	Output a value in Position Mode
04	Output a value in Position Mode
104	Output a value in Immediate Mode

Parameters	Description
Operand 1	The number, or memory address of the number, to output

05 - JUMP IF TRUE

06 - JUMP IF FALSE

07 - LESS THAN

08 - EQUALS

09 - MODIFY RELATIVE BASE

Takes one parameter as input, and adds that number to the stack's Relative Base Offset. This value may be either a positive or negative integer.

Parameters	Description
Operand 1	The number, or memory address of the number, to add to the Relative Base Offset

99 - HALT

A simple instruction with no parameters. Stops the computer from running any more instructions.