aoc2024/day-24/internal/one/solve.go

package one

import (
	"bytes"
	"math"
	"sort"
	"strings"
)

func Solve(buf []byte) (int, error) {
	r := bytes.NewReader(buf)
	wires, expressions, err := parseLines(r)
	if err != nil {
		return 0, err
	}

	wires = calculateWire(expressions, wires)
	zWires := filter(wires, func(name string) bool {
		return strings.HasPrefix(name, "z")
	})
	sort.Sort(byName(zWires))

	var decimal int
	for i, zWire := range zWires {
		decimal += zWire.value * int(math.Pow(float64(2), float64(i)))
	}

	return decimal, nil
}

func calculateWire(expressions []expression, wires map[string]int) map[string]int {
	if !anyNegative(wires) {
		return wires
	}

	for _, expression := range expressions {
		if wires[expression.left] != noValue && wires[expression.right] != noValue {
			switch expression.op {
			case AND:
				wires[expression.target] = wires[expression.left] & wires[expression.right]
			case OR:
				wires[expression.target] = wires[expression.left] | wires[expression.right]
			case XOR:
				wires[expression.target] = wires[expression.left] ^ wires[expression.right]
			}
		}
	}

	return calculateWire(expressions, wires)
}