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

package one

import (
	"bytes"
	"cmp"
	"slices"
	"strconv"
	"strings"

	log "github.com/sirupsen/logrus"
)

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

	for k, v := range initial {
		wires[k] = v
	}

	wires = calculateWire(expressions, wires)

	zWires := []zWire{}
	for k, v := range wires {
		if strings.HasPrefix(k, "z") {
			zWires = append(zWires, zWire{k, v})
		}
	}
	slices.SortFunc(zWires, func(a, b zWire) int {
		return cmp.Compare(b.name, a.name)
	})

	var binStr strings.Builder
	for _, zWire := range zWires {
		binStr.WriteString(strconv.FormatInt(int64(zWire.value), 2))
	}
	log.Debug(binStr.String())

	return mustConvBinToDec(binStr.String()), 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)
}