111 lines
1.9 KiB
Go
111 lines
1.9 KiB
Go
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package main
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import (
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"fmt"
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"sort"
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"strings"
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"aoc/helper"
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)
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type rules map[[2]int]struct{}
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type updates []update
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type update []int
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func main() {
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order_rules, page_updates := getOrdersAndUpdate()
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// part 1
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sum := 0
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for _, update := range page_updates {
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if update.validateRules(order_rules) {
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sum += update.getMiddleNumber()
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}
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}
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fmt.Printf("Summed updates: %d\n", sum)
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// part 2
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sum = 0
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for _, update := range page_updates {
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if update.validateRules(order_rules) {
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continue
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}
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update.reorderByRules(order_rules)
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if update.validateRules(order_rules) {
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sum += update.getMiddleNumber()
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}
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}
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fmt.Printf("Sum fixed updates: %d\n", sum)
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}
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func (u update) reorderByRules(r rules) update {
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sort.Slice(
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u,
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func(i, j int) bool {
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pair := [2]int{u[i], u[j]}
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if _, exists := r[pair]; exists {
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return true
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}
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pair = [2]int{u[j], u[i]}
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if _, exists := r[pair]; exists {
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return false
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}
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return false
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},
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)
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return u
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}
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func (u update) validateRules(r rules) bool {
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for i := 0; i < len(u)-1; i++ {
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// check if a rule exists for current page pair (this + next)
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pair := [2]int{u[i+1], u[i]}
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if _, exists := r[pair]; exists {
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return false
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}
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}
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return true
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}
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func (u update) getMiddleNumber() int {
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return u[len(u)/2]
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}
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func getOrdersAndUpdate() (rules, updates) {
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data := helper.GetLines()
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// parse rules
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rules := rules{}
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for data.Scan() {
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line := data.Text()
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if len(line) <= 1 {
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// empty line, leave the rest for the update parser
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break
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}
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parts := strings.Split(line, "|")
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page := helper.ToInt(parts[0])
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after := helper.ToInt(parts[1])
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rules[[2]int{page, after}] = struct{}{}
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}
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// parse updates
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updates := updates{}
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for data.Scan() {
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line := data.Text()
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parts := strings.Split(line, ",")
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update := update{}
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for _, part := range parts {
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update = append(update, helper.ToInt(part))
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}
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updates = append(updates, update)
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}
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return rules, updates
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}
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