AdventOfCode2020/10/main.go
2020-12-11 21:57:10 -05:00

123 lines
2.5 KiB
Go

package main
import (
"bufio"
"fmt"
"os"
"sort"
"strconv"
"time"
)
func main() {
start := time.Now()
partOne()
duration := time.Since(start)
partTwo()
duration2 := time.Since(start)
fmt.Printf("p1: %s, p2: %s\n", duration, duration2-duration)
}
// Find a chain that uses all of your adapters to connect the charging outlet to your device's built-in adapter
// and count the joltage differences between the charging outlet, the adapters, and your device.
// What is the number of 1-jolt differences multiplied by the number of 3-jolt differences?
func partOne() {
f, _ := os.Open("input")
reader := bufio.NewReader(f)
scanner := bufio.NewScanner(reader)
// wall
adapters := []int{0}
// load
for scanner.Scan() {
line := scanner.Text()
i, _ := strconv.Atoi(line)
adapters = append(adapters, i)
}
// sort
sort.Slice(adapters, func(i, j int) bool {
return adapters[i] < adapters[j]
})
// device
adapters = append(adapters, adapters[len(adapters)-1]+3)
one := 0
three := 0
// count gaps
for i, j := range adapters {
if i < len(adapters)-1 {
if adapters[i+1]-j == 3 {
three = three + 1
} else if adapters[i+1]-j == 1 {
one = one + 1
}
}
}
fmt.Println(three * one)
}
// You glance back down at your bag and try to remember why you brought so many adapters; there must be more than a trillion valid ways to arrange them!
// Surely, there must be an efficient way to count the arrangements.
// What is the total number of distinct ways you can arrange the adapters to connect the charging outlet to your device?
func partTwo() {
f, _ := os.Open("input")
reader := bufio.NewReader(f)
scanner := bufio.NewScanner(reader)
// wall
adapters := []int{0}
for scanner.Scan() {
line := scanner.Text()
i, _ := strconv.Atoi(line)
adapters = append(adapters, i)
}
// sort
sort.Slice(adapters, func(i, j int) bool {
return adapters[i] < adapters[j]
})
// device
adapters = append(adapters, adapters[len(adapters)-1]+3)
combinations := 1
ones := 0
three := 0
// count gaps
for i, j := range adapters {
if i < len(adapters)-1 {
if adapters[i+1]-j == 1 {
// small steps...
ones = ones + 1
} else if adapters[i+1]-j == 3 {
combinations = combinations + 1
if ones == 2 {
combinations = combinations * 1
}
if ones == 3 {
combinations = combinations * 2
}
if ones == 4 {
combinations = combinations * 4
}
if ones == 5 {
combinations = combinations * 7
}
ones = 0
three = three + 1
}
}
}
fmt.Println(adapters, combinations)
}