From dff0a314f2a08fb7e150c7f236b62596891b7db7 Mon Sep 17 00:00:00 2001
From: Scott McKendry <39483124+scottmckendry@users.noreply.github.com>
Date: Tue, 28 Nov 2023 16:54:59 +1300
Subject: [PATCH] Add 2022 Day 12 p2

---
 2022/12p1.go | 28 ++++++++++++++++++------
 2022/12p2.go | 60 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 2022/main.go |  1 +
 3 files changed, 82 insertions(+), 7 deletions(-)
 create mode 100644 2022/12p2.go

diff --git a/2022/12p1.go b/2022/12p1.go
index 4b3af46..69f5929 100644
--- a/2022/12p1.go
+++ b/2022/12p1.go
@@ -27,7 +27,11 @@ func D12P1() {
 	queue := []nodeCoordinate{}
 
 	// Append start node to queue
-	start := findStart(hills)
+	start := findStart(hills, false)
+	value, exists := hills[start]
+	if exists {
+		value.movesFromStart = 0
+	}
 	queue = append(queue, start)
 
 	for queue != nil {
@@ -41,7 +45,7 @@ func D12P1() {
 			break
 		}
 
-		neighbours := findNeighbours(&hills, queue[0])
+		neighbours := findNeighbours(&hills, queue[0], false)
 
 		for _, n := range neighbours {
 			value, exists := hills[n]
@@ -74,7 +78,6 @@ func parseHills(lines []string) map[nodeCoordinate]node {
 			if string(char) == "S" {
 				char = 'a'
 				start = true
-				movesFromStart = 0
 			}
 			if string(char) == "E" {
 				char = 'z'
@@ -95,16 +98,23 @@ func parseHills(lines []string) map[nodeCoordinate]node {
 	return hills
 }
 
-func findStart(hills map[nodeCoordinate]node) nodeCoordinate {
+func findStart(hills map[nodeCoordinate]node, reverse bool) nodeCoordinate {
 	for coordinate, hill := range hills {
-		if hill.start {
+		if hill.start && !reverse {
+			return coordinate
+		}
+		if hill.end && reverse {
 			return coordinate
 		}
 	}
 	return nodeCoordinate{}
 }
 
-func findNeighbours(hills *map[nodeCoordinate]node, coordinate nodeCoordinate) []nodeCoordinate {
+func findNeighbours(
+	hills *map[nodeCoordinate]node,
+	coordinate nodeCoordinate,
+	reverse bool,
+) []nodeCoordinate {
 	neighbours := []nodeCoordinate{}
 	posibleNeighbours := []nodeCoordinate{
 		{coordinate.x + 1, coordinate.y},
@@ -117,7 +127,11 @@ func findNeighbours(hills *map[nodeCoordinate]node, coordinate nodeCoordinate) [
 
 	for _, possibleNeighbour := range posibleNeighbours {
 		value, exists := (*hills)[possibleNeighbour]
-		if exists && value.value-currentHillValue > 1 {
+		if exists && value.value-currentHillValue > 1 && !reverse {
+			continue
+		}
+
+		if exists && currentHillValue-value.value > 1 && reverse {
 			continue
 		}
 
diff --git a/2022/12p2.go b/2022/12p2.go
new file mode 100644
index 0000000..4634ae3
--- /dev/null
+++ b/2022/12p2.go
@@ -0,0 +1,60 @@
+package main
+
+import (
+	"fmt"
+
+	"aoc2022/utils"
+)
+
+func D12P2() {
+	lines := utils.ReadLines("./inputs/12.txt")
+	hills := parseHills(lines)
+
+	queue := []nodeCoordinate{}
+
+	end := findStart(hills, true)
+	value, exists := hills[end]
+	if exists {
+		value.movesFromStart = 0
+	}
+	hills[end] = value
+	queue = append(queue, end)
+
+	bestRoute := int(^uint(0) >> 1)
+
+	for len(queue) > 0 {
+		if hills[queue[0]].visited {
+			queue = queue[1:]
+			continue
+		}
+
+		if hills[queue[0]].letter == "a" {
+			if hills[queue[0]].movesFromStart < bestRoute {
+				bestRoute = hills[queue[0]].movesFromStart
+			}
+		}
+
+		neighbours := findNeighbours(&hills, queue[0], true)
+
+		for _, n := range neighbours {
+			value, exists := hills[n]
+
+			if exists {
+				value.movesFromStart = updateMovesFromStart(value, hills[queue[0]])
+				hills[n] = value
+			}
+
+			queue = append(queue, n)
+		}
+
+		value, exists := hills[queue[0]]
+		if exists {
+			value.visited = true
+			hills[queue[0]] = value
+		}
+		queue = queue[1:]
+
+	}
+
+	fmt.Printf("Best route: %d\n", bestRoute)
+}
diff --git a/2022/main.go b/2022/main.go
index 2279fd1..14242c4 100644
--- a/2022/main.go
+++ b/2022/main.go
@@ -34,6 +34,7 @@ var solutions = map[string]func(){
 	"11P1:Monkey in the Middle":    D11P1,
 	"11P2:Monkey in the Middle":    D11P2,
 	"12P1:Hill Climbing Algorithm": D12P1,
+	"12P2:Hill Climbing Algorithm": D12P2,
 }
 
 func main() {