I did the last part by hand first, then bothered to write out the reduction loop
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353d5e92c9
commit
0883efd35e
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@ -0,0 +1,229 @@
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package main
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import (
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"bufio"
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"fmt"
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"os"
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"strconv"
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"strings"
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"time"
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)
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func main() {
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start := time.Now()
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partOne()
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duration := time.Since(start)
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partTwo()
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duration2 := time.Since(start)
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fmt.Printf("p1: %s, p2: %s\n", duration, duration2-duration)
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}
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type valuerange struct {
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min int
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max int
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}
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type rule struct {
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name string
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ranges []valuerange
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field int
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}
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type ticket struct {
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values []int
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valid bool
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}
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func parseRule(s string) rule {
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q := strings.Split(s, ": ")
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ru := rule{
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name: q[0],
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ranges: make([]valuerange, 0, 2),
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}
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r := strings.Split(q[1], " or ")
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for _, rr := range r {
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mm := strings.Split(rr, "-")
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min, _ := strconv.Atoi(mm[0])
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max, _ := strconv.Atoi(mm[1])
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ru.ranges = append(ru.ranges, valuerange{min: min, max: max})
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}
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return ru
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}
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func parseTicket(s string) ticket {
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t := ticket{
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values: []int{},
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}
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vs := strings.Split(s, ",")
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for _, v := range vs {
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vi, _ := strconv.Atoi(v)
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t.values = append(t.values, vi)
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}
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return t
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}
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// return valid/invalid and the invalid value, if found
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func validateTicket(r []rule, t ticket) (bool, int) {
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for _, ta := range t.values {
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ok := false
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for _, ru := range r {
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outsideRule := (ta < ru.ranges[0].min || (ta > ru.ranges[0].max && ta < ru.ranges[1].min) || ta > ru.ranges[1].max)
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if ok || !outsideRule {
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ok = true
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}
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}
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if !ok {
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return false, ta
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}
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}
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return true, 0
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}
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// returns a mapping of fields to possible rules
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func guessFields(rules []rule, tickets []ticket) map[int][]int {
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guesses := map[int][]int{}
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for ri, r := range rules {
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for i := range tickets[0].values { // loop over the fields on tickets, and...
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ok := true
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for _, t := range tickets { // loop over all the tickets...
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ta := t.values[i] // checking the current field value...
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outsideRule := (ta < r.ranges[0].min || (ta > r.ranges[0].max && ta < r.ranges[1].min) || ta > r.ranges[1].max)
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if !ok || outsideRule { // checking if any of the tickets fall outside our rule's range.
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ok = false
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}
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}
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if ok { // if all tickets pass, we've got a hit
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guesses[i] = append(guesses[i], ri)
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}
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}
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}
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return guesses
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}
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func reduce(g map[int][]int) (int, int) {
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for i, j := range g {
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if len(j) == 1 {
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return i, j[0]
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}
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}
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return 0, 0
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}
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func remove(a []int, rule int) []int {
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for i, j := range a {
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if j == rule {
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a[i] = a[len(a)-1]
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a[len(a)-1] = 0
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return a[:len(a)-1]
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}
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}
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return a
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}
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func partOne() {
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f, _ := os.Open("input")
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reader := bufio.NewReader(f)
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scanner := bufio.NewScanner(reader)
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rules := []rule{}
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tickets := []ticket{}
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invalidityRate := 0
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seenAllRules := false
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seenMyTicket := false
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for scanner.Scan() {
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line := scanner.Text()
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// check for end of rules list
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if line == "" && !seenAllRules {
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seenAllRules = true
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scanner.Scan() // clear out the following line
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continue
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}
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// parse rules until we run out
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if !seenAllRules {
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rules = append(rules, parseRule(line))
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continue
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}
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// parse own ticket, then clear for remaining tickets
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if !seenMyTicket {
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tickets = append(tickets, parseTicket(scanner.Text()))
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seenMyTicket = true
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scanner.Scan() // clear out the next two lines
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scanner.Scan()
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continue
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}
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// parse and validate other people's tickets
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t := parseTicket(line)
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ok, i := validateTicket(rules, t)
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if !ok {
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t.valid = false
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invalidityRate = invalidityRate + i
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} else {
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t.valid = true
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tickets = append(tickets, t)
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}
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}
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fmt.Println(invalidityRate)
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}
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func partTwo() {
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f, _ := os.Open("input")
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reader := bufio.NewReader(f)
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scanner := bufio.NewScanner(reader)
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rules := []rule{}
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myTicket := ticket{}
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tickets := []ticket{}
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seenAllRules := false
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seenMyTicket := false
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for scanner.Scan() {
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line := scanner.Text()
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// check for end of rules list
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if line == "" && !seenAllRules {
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seenAllRules = true
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scanner.Scan() // clear out the following line
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continue
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}
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// parse rules until we run out
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if !seenAllRules {
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rules = append(rules, parseRule(line))
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continue
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}
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// parse own ticket, then clear for remaining tickets
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if !seenMyTicket {
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myTicket = parseTicket(scanner.Text())
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tickets = append(tickets, myTicket)
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seenMyTicket = true
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scanner.Scan() // clear out the next two lines
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scanner.Scan()
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continue
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}
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// parse and validate other people's tickets
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t := parseTicket(line)
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ok, _ := validateTicket(rules, t)
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if ok {
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t.valid = true
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tickets = append(tickets, t)
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}
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}
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guesses := guessFields(rules, tickets)
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var lastRuleSolved int
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for i := 1; i < len(guesses); i++ {
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for i, g := range guesses {
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if len(g) == 1 {
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rules[g[0]].field = i
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lastRuleSolved = g[0]
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}
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}
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for i := range guesses {
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guesses[i] = remove(guesses[i], lastRuleSolved)
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}
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}
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result := 1
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// first 6 rules are our "departure" rules
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for _, r := range rules[:6] {
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result = result * myTicket.values[r.field]
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}
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fmt.Println(result)
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}
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