2021 Day 12 Complete!

2021/day12/main.go

@@ -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())
+	}
+}