adventofcode/2024/day24/main.go

package main

import (
	"fmt"
	"sort"
	"strconv"
	"strings"

	h "git.bullercodeworks.com/brian/adventofcode/helpers"
)

func main() {
	inp := h.StdinToStringSlice()
	part1(inp)
	fmt.Println()
	part2(inp)
}

func part1(inp []string) {
	fmt.Println("# Part 1")
	dev, gates := parseInput1(inp)
	// Perform all logic
	gateDone := make(map[int]bool)
	for len(gateDone) != len(gates)-1 {
		for i := range gates {
			if _, ok := gateDone[i]; !ok {
				pts := strings.Split(gates[i], " ")
				var w1, w2, ok bool
				if w1, ok = dev[pts[0]]; ok {
					if w2, ok = dev[pts[2]]; ok {
						switch pts[1] {
						case "AND":
							dev[pts[4]] = w1 && w2
						case "OR":
							dev[pts[4]] = w1 || w2
						case "XOR":
							dev[pts[4]] = w1 != w2
						}
						gateDone[i] = true
					}
				}
			}
		}
	}
	fmt.Println(findValueOf(dev, "z"))
}

// Not fully working yet... I solved this part manually.
func part2(inp []string) {
	fmt.Println("# Part 2")
	gates := parseInput2(inp)[1]

	var swapped []string
	var c0 string

	for i := 0; i < 45; i++ {
		n := fmt.Sprintf("%02d", i)
		var m1, n1, r1, z1, c1 string

		m1 = find("x"+n, "y"+n, "XOR", gates)
		n1 = find("x"+n, "y"+n, "AND", gates)

		if c0 != "" {
			r1 = find(c0, m1, "AND", gates)
			if r1 == "" {
				m1, n1 = n1, m1
				swapped = append(swapped, m1, n1)
				r1 = find(c0, m1, "AND", gates)
			}

			z1 = find(c0, m1, "XOR", gates)

			if strings.HasPrefix(m1, "z") {
				m1, z1 = z1, m1
				swapped = append(swapped, m1, z1)
			}

			if strings.HasPrefix(n1, "z") {
				n1, z1 = z1, n1
				swapped = append(swapped, n1, z1)
			}

			if strings.HasPrefix(r1, "z") {
				r1, z1 = z1, r1
				swapped = append(swapped, r1, z1)
			}

			c1 = find(r1, n1, "OR", gates)
		}

		if strings.HasPrefix(c1, "z") && c1 != "z45" {
			c1, z1 = z1, c1
			swapped = append(swapped, c1, z1)
		}

		if c0 == "" {
			c0 = n1
		} else {
			c0 = c1
		}
	}

	// Sort and join swapped wires
	sort.Strings(swapped)
	fmt.Println(strings.Join(swapped, ","))
}

func parseInput1(inp []string) (map[string]bool, []string) {
	dev := make(map[string]bool)
	var gates []string
	var inGates bool
	for i := range inp {
		if len(inp[i]) == 0 {
			inGates = true
		}
		if !inGates {
			if inp[i][3] == ':' {
				wire := inp[i][:3]
				v := inp[i][5] == '1'
				dev[wire] = v
			}
		} else {
			gates = append(gates, inp[i])
		}
	}
	return dev, gates
}

func parseInput2(inp []string) [][]string {
	var parts [][]string
	var currPt []string
	for _, line := range inp {
		if line == "" {
			if len(currPt) > 0 {
				parts = append(parts, currPt)
				currPt = []string{}
			}
		} else {
			currPt = append(currPt, line)
		}
	}
	if len(currPt) > 0 {
		parts = append(parts, currPt)
	}
	return parts
}

func findHighestReg(dev map[string]bool) int {
	var highest string
	for i := range dev {
		if i > highest {
			highest = i
		}
	}
	ret, _ := strconv.Atoi(highest[1:])
	return ret
}

func findValueOf(dev map[string]bool, register string) int64 {
	var highest string
	for i := range dev {
		if i > highest {
			highest = i
		}
	}
	get, _ := strconv.Atoi(highest[1:])
	var val int64
	for i := get; ; i-- {
		key := fmt.Sprintf("%s%02d", register, i)
		v, ok := dev[key]
		if !ok {
			break
		} else {
			val = val << 1
			if v {
				val += 1
			}
		}
	}
	return val
}

func find(w1, w2, op string, gates []string) string {
	for _, gate := range gates {
		if strings.HasPrefix(gate, fmt.Sprintf("%s %s %s", w1, op, w2)) ||
			strings.HasPrefix(gate, fmt.Sprintf("%s %s %s", w2, op, w2)) {
			parts := strings.Split(gate, " -> ")
			return parts[len(parts)-1]
		}
	}
	return ""
}