Day10

2024/gareth/day10/day10.go

@@ -0,0 +1,141 @@
+package day10
+
+import (
+	"strings"
+)
+
+var directions = [][2]int{
+	{-1, 0},
+	{1, 0},
+	{0, -1},
+	{0, 1},
+}
+
+func Part1(input string) int {
+	grid := ParseInput(input)
+	return CalculateTotalTrailheadScore(grid)
+}
+
+func Part2(input string) int {
+	grid := ParseInput(input)
+	return CalculateTotalTrailheadRating(grid)
+}
+
+func ParseInput(input string) [][]int {
+	lines := strings.Split(strings.TrimSpace(input), "\n")
+	grid := make([][]int, len(lines))
+	for i, line := range lines {
+		grid[i] = make([]int, len(line))
+		for j, char := range line {
+			grid[i][j] = int(char - '0')
+		}
+	}
+	return grid
+}
+
+func IsValidPosition(x, y, rows, cols int) bool {
+	return x >= 0 && x < rows && y >= 0 && y < cols
+}
+
+func DFS(grid [][]int, x, y, prevHeight int, visited [][]bool, reached9 map[[2]int]bool) {
+	rows := len(grid)
+	cols := len(grid[0])
+	if !IsValidPosition(x, y, rows, cols) || visited[x][y] || grid[x][y] != prevHeight+1 {
+		return
+	}
+
+	if grid[x][y] == 9 {
+		reached9[[2]int{x, y}] = true
+		return
+	}
+
+	visited[x][y] = true
+	for _, dir := range directions {
+		nx, ny := x+dir[0], y+dir[1]
+		DFS(grid, nx, ny, grid[x][y], visited, reached9)
+	}
+	visited[x][y] = false
+}
+
+func CalculateTrailheadScore(grid [][]int, x, y int) int {
+	rows := len(grid)
+	cols := len(grid[0])
+	visited := make([][]bool, rows)
+	for i := range visited {
+		visited[i] = make([]bool, cols)
+	}
+
+	reached9 := make(map[[2]int]bool)
+	DFS(grid, x, y, -1, visited, reached9)
+	return len(reached9)
+}
+
+func DFSForRatings(grid [][]int, x, y, prevHeight int, visited [][]bool, trailCache map[[3]int]int) int {
+	rows := len(grid)
+	cols := len(grid[0])
+	if !IsValidPosition(x, y, rows, cols) || visited[x][y] || grid[x][y] != prevHeight+1 {
+		return 0
+	}
+
+	if grid[x][y] == 9 {
+		return 1
+	}
+
+	cacheKey := [3]int{x, y, grid[x][y]}
+	if count, exists := trailCache[cacheKey]; exists {
+		return count
+	}
+
+	visited[x][y] = true
+	totalTrails := 0
+	for _, dir := range directions {
+		nx, ny := x+dir[0], y+dir[1]
+		totalTrails += DFSForRatings(grid, nx, ny, grid[x][y], visited, trailCache)
+	}
+	visited[x][y] = false
+
+	trailCache[cacheKey] = totalTrails
+	return totalTrails
+}
+
+func CalculateTrailheadRating(grid [][]int, x, y int) int {
+	rows := len(grid)
+	cols := len(grid[0])
+	visited := make([][]bool, rows)
+	for i := range visited {
+		visited[i] = make([]bool, cols)
+	}
+
+	trailCache := make(map[[3]int]int)
+	return DFSForRatings(grid, x, y, -1, visited, trailCache)
+}
+
+func CalculateTotalTrailheadScore(grid [][]int) int {
+	rows := len(grid)
+	cols := len(grid[0])
+	totalScore := 0
+	for i := 0; i < rows; i++ {
+		for j := 0; j < cols; j++ {
+			if grid[i][j] == 0 {
+				score := CalculateTrailheadScore(grid, i, j)
+				totalScore += score
+			}
+		}
+	}
+	return totalScore
+}
+
+func CalculateTotalTrailheadRating(grid [][]int) int {
+	rows := len(grid)
+	cols := len(grid[0])
+	totalRating := 0
+	for i := 0; i < rows; i++ {
+		for j := 0; j < cols; j++ {
+			if grid[i][j] == 0 {
+				rating := CalculateTrailheadRating(grid, i, j)
+				totalRating += rating
+			}
+		}
+	}
+	return totalRating
+}

2024/gareth/day10/day10_test.go

@@ -0,0 +1,31 @@
+package day10
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestPart1(t *testing.T) {
+	r := Part1(`89010123
+78121874
+87430965
+96549874
+45678903
+32019012
+01329801
+10456732`)
+	assert.Equal(t, 36, r)
+}
+
+func TestPart2(t *testing.T) {
+	r := Part2(`89010123
+78121874
+87430965
+96549874
+45678903
+32019012
+01329801
+10456732`)
+	assert.Equal(t, 81, r)
+}

2024/gareth/day10/input.txt

@@ -0,0 +1,45 @@
+987123434330121232101001234730123456781067632
+876076576521010345692340349823212347892398701
+945087689432105676787659856714503210987445610
+332196576587654989801456787609654502376530923
+211543210298923215432321098128778901430121894
+300692340147210106523543210039569876589836765
+456781678236103267015693016543410231276745650
+576890549345234178106782187612320140345654321
+985098432100125089235493498109876056034765012
+834127102345456978340362569018765487123876678
+123236221976347869651251078729034398101985589
+014545340889298958707867897430120987012834432
+105965456770107843216950956541231276543124501
+896872378761016930345441019876501345678023670
+787901069654325321210332398545432330589012981
+107821543213034321089206787638901421432103210
+215430694102123475670115896129876548901210349
+126989780210014984308924925014578037654321458
+037878921001235675217833210123669123109452367
+549865438901045102346542106548754321278501476
+678954987432696201256430087239689870347699985
+230143006501787349961021298101236787656788014
+123272112981010458872787034010345691875107623
+054387623472129867763698125676210010961234510
+565694502561036789854567012980387121250129878
+676783411051045672343218763901296030343278569
+989872123432345891050109654812345145467303450
+012763094321056700891760345765432256958912341
+103450185789763211709851236876301967843211032
+814321276656854345612345654954101878701208983
+923434434565956745678036783063210989870345674
+874532345410345832989123192178981876781456564
+265101654323234901808765013265432185692387565
+103216765432101267814554323476501094501893474
+232109856321011876923601098789678923432102985
+343898707896540945498712367765672310567891078
+456789010987231234321203456894581455454986569
+556776125670102343100157654503490166303890432
+543895434894321765212348983212321876212761201
+432104898765010894301054581200110955211654300
+301256567656987105498765690341034567300563212
+434567430547896234787654785652123498456767843
+321798121032345375696543098743096567877854952
+210899021121036789781232143456787656928923761
+326765430110145678710123232109876543210010890

2024/gareth/main.go

@@ -1,7 +1,7 @@
 package main
 
 import (
-	"aoc2024/day19"
+	"aoc2024/day10"
 	"fmt"
 	"os"
 	"time"
@@ -9,9 +9,9 @@ import (
 
 func main() {
 	start := time.Now()
-	data, _ := os.ReadFile("day19/input.txt")
-	fmt.Printf("part 1: %d\n", day19.Part1(string(data)))
-	fmt.Printf("part 2: %d\n", day19.Part2(string(data)))
+	data, _ := os.ReadFile("day10/input.txt")
+	fmt.Printf("part 1: %d\n", day10.Part1(string(data)))
+	fmt.Printf("part 2: %d\n", day10.Part2(string(data)))
 	elapsed := time.Since(start)
 	fmt.Printf("Execution time: %s\n", elapsed)
 }