brian/adventofcode
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

2021 Day 12 Complete!

Browse Source
This commit is contained in:
Brian Buller 2021-12-12 09:17:41 -06:00
parent 6c3dc59afc
commit 00f1bff786
6 changed files with 405 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

23
2021/day12/input Normal file
View File

@ -0,0 +1,23 @@
pn-TY
rp-ka
az-aw
al-IV
pn-co
end-rp
aw-TY
rp-pn
al-rp
end-al
IV-co
end-TM
co-TY
TY-ka
aw-pn
aw-IV
pn-IV
IV-ka
TM-rp
aw-PD
start-IV
start-co
start-pn

158
2021/day12/main.go Normal file
View File

@ -0,0 +1,158 @@
package main
import (
"fmt"
"strings"
h "git.bullercodeworks.com/brian/adventofcode/helpers"
)
func main() {
inp := h.StdinToStringSlice()
part1(BuildCaves(inp))
fmt.Println()
part2(BuildCaves(inp))
}
func BuildCaves(inp []string) map[string]Cave {
ret := make(map[string]Cave)
for i := range inp {
pts := strings.Split(inp[i], "-")
var c1, c2 Cave
var ok bool
if c1, ok = ret[pts[0]]; !ok {
c1 = NewCave(pts[0])
}
if c2, ok = ret[pts[1]]; !ok {
c2 = NewCave(pts[1])
}
if !c1.ExitsTo(c2) {
c1.Exits = append(c1.Exits, c2.Name)
}
if !c2.ExitsTo(c1) {
c2.Exits = append(c2.Exits, c1.Name)
}
ret[c1.Name] = c1
ret[c2.Name] = c2
}
return ret
}
func part1(inp map[string]Cave) {
curr, _ := inp["start"]
res := part1_findPaths([]Cave{curr}, inp)
fmt.Println("# Part 1")
fmt.Println("There are", len(res), "paths")
}
func part1_shouldVisit(c string, path []Cave) bool {
if c[0] < 'A' || c[0] > 'Z' {
for i := range path {
if path[i].Name == c {
return false
}
}
}
return true
}
func part1_findPaths(path []Cave, system map[string]Cave) [][]Cave {
var ret [][]Cave
curr := path[len(path)-1]
if curr.Name == "end" {
return append(ret, path)
}
for _, c := range curr.Exits {
if part1_shouldVisit(c, path) {
newPaths := part1_findPaths(append(path, system[c]), system)
ret = append(ret, newPaths...)
}
}
return ret
}
func part2(inp map[string]Cave) {
curr, _ := inp["start"]
res := part2_findPaths([]Cave{curr}, inp)
fmt.Println("# Part 2")
fmt.Println("There are", len(res), "paths")
}
func part2_shouldVisit(c string, path []Cave) bool {
if path[len(path)-1].Name == "end" {
// If the previous spot was end, we shouldn't visit anything
return false
}
if c[0] < 'A' || c[0] > 'Z' {
if c == "start" { // We never return to start
return false
}
// Check if we've already visited this cave
visits := make(map[string]int)
var visited, twice bool
for i := range path {
if path[i].Name == c {
visited = true
}
visits[path[i].Name]++
if !path[i].Big && visits[path[i].Name] > 1 {
twice = true
}
}
if visited && twice {
return false
}
}
return true
}
func part2_findPaths(path []Cave, system map[string]Cave) [][]Cave {
var ret [][]Cave
curr := path[len(path)-1]
if curr.Name == "end" {
return append(ret, path)
}
for _, c := range curr.Exits {
if part2_shouldVisit(c, path) {
newPaths := part2_findPaths(append(path, system[c]), system)
ret = append(ret, newPaths...)
}
}
return ret
}
type Cave struct {
Name string
Big bool
Exits []string
}
func NewCave(n string) Cave {
return Cave{
Name: n,
Big: (n[0] >= 'A' && n[0] <= 'Z'),
}
}
func (c Cave) ExitsTo(e Cave) bool {
for i := range c.Exits {
if c.Exits[i] == e.Name {
return true
}
}
return false
}
func (c Cave) String() string {
return c.Name
}
func (c Cave) Detail() string {
return fmt.Sprintf("{%s -> %s}", c.Name, c.Exits)
}
func PrintMap(inp map[string]Cave) {
for k := range inp {
fmt.Println(inp[k].Detail())
}
}

189
2021/day12/problem Normal file
View File

@ -0,0 +1,189 @@
# Advent of Code
--- Day 12: Passage Pathing ---
With your submarine's subterranean subsystems subsisting suboptimally, the only way you're getting out of this cave anytime soon is by finding a
path yourself. Not just a path - the only way to know if you've found the best path is to find all of them.
Fortunately, the sensors are still mostly working, and so you build a rough map of the remaining caves (your puzzle input). For example:
start-A
start-b
A-c
A-b
b-d
A-end
b-end
This is a list of how all of the caves are connected. You start in the cave named start, and your destination is the cave named end. An entry
like b-d means that cave b is connected to cave d - that is, you can move between them.
So, the above cave system looks roughly like this:
start
/ \
c--A-----b--d
\ /
end
Your goal is to find the number of distinct paths that start at start, end at end, and don't visit small caves more than once. There are two
types of caves: big caves (written in uppercase, like A) and small caves (written in lowercase, like b). It would be a waste of time to visit any
small cave more than once, but big caves are large enough that it might be worth visiting them multiple times. So, all paths you find should
visit small caves at most once, and can visit big caves any number of times.
Given these rules, there are 10 paths through this example cave system:
start,A,b,A,c,A,end
start,A,b,A,end
start,A,b,end
start,A,c,A,b,A,end
start,A,c,A,b,end
start,A,c,A,end
start,A,end
start,b,A,c,A,end
start,b,A,end
start,b,end
(Each line in the above list corresponds to a single path; the caves visited by that path are listed in the order they are visited and separated
by commas.)
Note that in this cave system, cave d is never visited by any path: to do so, cave b would need to be visited twice (once on the way to cave d
and a second time when returning from cave d), and since cave b is small, this is not allowed.
Here is a slightly larger example:
dc-end
HN-start
start-kj
dc-start
dc-HN
LN-dc
HN-end
kj-sa
kj-HN
kj-dc
The 19 paths through it are as follows:
start,HN,dc,HN,end
start,HN,dc,HN,kj,HN,end
start,HN,dc,end
start,HN,dc,kj,HN,end
start,HN,end
start,HN,kj,HN,dc,HN,end
start,HN,kj,HN,dc,end
start,HN,kj,HN,end
start,HN,kj,dc,HN,end
start,HN,kj,dc,end
start,dc,HN,end
start,dc,HN,kj,HN,end
start,dc,end
start,dc,kj,HN,end
start,kj,HN,dc,HN,end
start,kj,HN,dc,end
start,kj,HN,end
start,kj,dc,HN,end
start,kj,dc,end
Finally, this even larger example has 226 paths through it:
fs-end
he-DX
fs-he
start-DX
pj-DX
end-zg
zg-sl
zg-pj
pj-he
RW-he
fs-DX
pj-RW
zg-RW
start-pj
he-WI
zg-he
pj-fs
start-RW
How many paths through this cave system are there that visit small caves at most once?
Your puzzle answer was 4413.
--- Part Two ---
After reviewing the available paths, you realize you might have time to visit a single small cave twice. Specifically, big caves can be visited
any number of times, a single small cave can be visited at most twice, and the remaining small caves can be visited at most once. However, the
caves named start and end can only be visited exactly once each: once you leave the start cave, you may not return to it, and once you reach the
end cave, the path must end immediately.
Now, the 36 possible paths through the first example above are:
start,A,b,A,b,A,c,A,end
start,A,b,A,b,A,end
start,A,b,A,b,end
start,A,b,A,c,A,b,A,end
start,A,b,A,c,A,b,end
start,A,b,A,c,A,c,A,end
start,A,b,A,c,A,end
start,A,b,A,end
start,A,b,d,b,A,c,A,end
start,A,b,d,b,A,end
start,A,b,d,b,end
start,A,b,end
start,A,c,A,b,A,b,A,end
start,A,c,A,b,A,b,end
start,A,c,A,b,A,c,A,end
start,A,c,A,b,A,end
start,A,c,A,b,d,b,A,end
start,A,c,A,b,d,b,end
start,A,c,A,b,end
start,A,c,A,c,A,b,A,end
start,A,c,A,c,A,b,end
start,A,c,A,c,A,end
start,A,c,A,end
start,A,end
start,b,A,b,A,c,A,end
start,b,A,b,A,end
start,b,A,b,end
start,b,A,c,A,b,A,end
start,b,A,c,A,b,end
start,b,A,c,A,c,A,end
start,b,A,c,A,end
start,b,A,end
start,b,d,b,A,c,A,end
start,b,d,b,A,end
start,b,d,b,end
start,b,end
The slightly larger example above now has 103 paths through it, and the even larger example now has 3509 paths through it.
Given these new rules, how many paths through this cave system are there?
Your puzzle answer was 118803.
Both parts of this puzzle are complete! They provide two gold stars: **
At this point, you should return to your Advent calendar and try another puzzle.
If you still want to see it, you can get your puzzle input.
References
Visible links
. https://adventofcode.com/
. https://adventofcode.com/2021/about
. https://adventofcode.com/2021/events
. https://adventofcode.com/2021/settings
. https://adventofcode.com/2021/auth/logout
. Advent of Code Supporter
https://adventofcode.com/2021/support
. https://adventofcode.com/2021
. https://adventofcode.com/2021
. https://adventofcode.com/2021/support
. https://adventofcode.com/2021/sponsors
. https://adventofcode.com/2021/leaderboard
. https://adventofcode.com/2021/stats
. https://adventofcode.com/2021/sponsors
. https://adventofcode.com/2021
. https://adventofcode.com/2021/day/12/input

7
2021/day12/testinput Normal file
View File

@ -0,0 +1,7 @@
start-A
start-b
A-c
A-b
b-d
A-end
b-end

10
2021/day12/testinput2 Normal file
View File

@ -0,0 +1,10 @@
dc-end
HN-start
start-kj
dc-start
dc-HN
LN-dc
HN-end
kj-sa
kj-HN
kj-dc

18
2021/day12/testinput3 Normal file
View File

@ -0,0 +1,18 @@
fs-end
he-DX
fs-he
start-DX
pj-DX
end-zg
zg-sl
zg-pj
pj-he
RW-he
fs-DX
pj-RW
zg-RW
start-pj
he-WI
zg-he
pj-fs
start-RW