aoc day 7.1

day7.go

package aoc

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

func makeCircuit(s string) map[string]string {
	m := make(map[string]string)

	arr := strings.Split(s, "\n")

	r1 := regexp.MustCompile("([0-9a-zA-Z ]*) -> ([a-z]*)")

	for _, val := range arr {
		if len(val) == 0 {
			continue
		}

		// split (ANYTHING) -> [a-z]
		matches := r1.FindStringSubmatch(val)
		m[matches[2]] = matches[1]
	}

	return m
}

func resolveValue(m map[string]string, wire string) (uint16, map[string]string) {

	// fmt.Printf("processing %s\n", wire)

	var res uint16
	if len(wire) == 0 {
		fmt.Printf("XXX should not happen, empty input!\n")
		return 0, m
	}

	tokens := strings.Split(m[wire], " ")
	// fmt.Println(tokens)

	u, err := strconv.ParseUint(wire, 0, 16)
	if err == nil {
		// if number, return directly
		return uint16(u), m
	}

	if len(tokens) == 1 {
		res, m = resolveValue(m, tokens[0])
		m[wire] = fmt.Sprintf("%d", res)
		return res, m
	}

	if len(tokens) == 2 {
		// NOT
		//fmt.Printf("NOT   %s\n", tokens[1])
		res, m = resolveValue(m, tokens[1])
		res = 65535 - res
		m[wire] = fmt.Sprintf("%d", res)
		return res, m
	}

	op := tokens[1]

	a, m := resolveValue(m, tokens[0])
	b, m := resolveValue(m, tokens[2])

	switch op {
	case "LSHIFT":
		res = a << b
		m[wire] = fmt.Sprintf("%d", res)
		break
	case "RSHIFT":
		res = a >> b
		m[wire] = fmt.Sprintf("%d", res)
		break
	case "AND":
		res = a & b
		m[wire] = fmt.Sprintf("%d", res)
		break
	case "OR":
		res = a | b
		m[wire] = fmt.Sprintf("%d", res)
		break
	}

	return res, m
}

day7_test.go

package aoc

import (
	"io/ioutil"
	"testing"

	"github.com/stretchr/testify/assert"
)

func TestMakeCircuit(t *testing.T) {

	c := makeCircuit(
		"123 -> x\n" +
			"456 -> y\n" +
			"x AND y -> d\n" +
			"x OR y -> e\n" +
			"x LSHIFT 2 -> f\n" +
			"y RSHIFT 2 -> g\n" +
			"NOT x -> h\n" +
			"NOT y -> i\n")

	res, c := resolveValue(c, "i")
	assert.Equal(t, uint16(65079), res)
}

func TestDay7Questions(t *testing.T) {
	data, err := ioutil.ReadFile("../day7_input")
	if err != nil {
		t.Fatal("Error ", err)
	}
	s := string(data)

	circuit := makeCircuit(s)

	a, _ := resolveValue(circuit, "a")

	// part 1
	assert.Equal(t, uint16(46065), a)
}