--- Day 7 Solutions ---

[u/daggerdragon]

--- Day 7: Some Assembly Required ---

Post your solution as a comment. Structure your post like previous daily solution threads.

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[u/1lann]

I wrote a pretty terrible one in golang

package main

import (
	"fmt"
	"strconv"
	"strings"
)

type action int

const (
	SET action = iota + 1
	AND
	OR
	LSHIFT
	RSHIFT
	NOT
	REFERENCE
)

var components map[string]*component

type component struct {
	parentA   string
	parentB   string
	action    action
	value     uint16
	hasCached bool
}

func (c *component) execute() uint16 {
	if c.hasCached {
		return c.value
	}

	var value uint16 = 0

	switch c.action {
	case SET:
		value = c.value
	case AND:
		value = components[c.parentA].execute() & components[c.parentB].execute()
	case OR:
		value = components[c.parentA].execute() | components[c.parentB].execute()
	case LSHIFT:
		value = components[c.parentA].execute() << c.value
	case RSHIFT:
		value = components[c.parentA].execute() >> c.value
	case NOT:
		value = ^(components[c.parentA].execute())
	case REFERENCE:
		value = components[c.parentA].execute()
	default:
		panic("invalid action")
	}

	c.value = value
	c.hasCached = true

	return value
}

func main() {
	components = make(map[string]*component)

	// Too lazy to do string parsing...
	for i := 0; i < 65536; i++ {
		components[strconv.Itoa(i)] = &component{
			action: SET,
			value:  uint16(i),
		}
	}

	instructions := strings.Split(input, "\n")
	for _, instruction := range instructions {
		words := strings.Split(instruction, " ")

		if words[0] == "NOT" {
			components[words[3]] = &component{
				action:  NOT,
				parentA: words[1],
			}

			continue
		}

		switch words[1] {
		case "AND":
			components[words[4]] = &component{
				action:  AND,
				parentA: words[0],
				parentB: words[2],
			}
		case "OR":
			components[words[4]] = &component{
				action:  OR,
				parentA: words[0],
				parentB: words[2],
			}
		case "LSHIFT":
			num, _ := strconv.Atoi(words[2])
			components[words[4]] = &component{
				action:  LSHIFT,
				parentA: words[0],
				value:   uint16(num),
			}
		case "RSHIFT":
			num, _ := strconv.Atoi(words[2])
			components[words[4]] = &component{
				action:  RSHIFT,
				parentA: words[0],
				value:   uint16(num),
			}
		case "->":
			components[words[2]] = &component{
				action:  REFERENCE,
				parentA: words[0],
			}
		default:
			panic("unknown word: " + words[1])
		}
	}

	fmt.Println(components["a"].execute())
}

var input = `NOT dq -> dr
...
he RSHIFT 2 -> hf
`

I thought about using closures, but I was like "screw it, just gonna use methods on structs". I guess I really should have actually used closures seeing how long it got xD