[2024] Solution for Day 10

Author: kfarnung

2024/day10/main.go

@@ -0,0 +1,97 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+
+	"github.com/kfarnung/advent-of-code/2024/lib"
+)
+
+func part1(input string) int64 {
+	topoMap, trailHeads := parseMap(input)
+	sum := int64(0)
+	for _, trailHead := range trailHeads {
+		terminalPositions := make(map[lib.Point2D]bool)
+		findTerminalPositions(topoMap, trailHead, terminalPositions)
+
+		sum += int64(len(terminalPositions))
+	}
+
+	return sum
+}
+
+func part2(input string) int64 {
+	topoMap, trailHeads := parseMap(input)
+	sum := int64(0)
+	for _, trailHead := range trailHeads {
+		terminalPositions := make(map[lib.Point2D]bool)
+		sum += findTerminalPositions(topoMap, trailHead, terminalPositions)
+	}
+
+	return sum
+}
+
+func findTerminalPositions(topoMap [][]rune, position lib.Point2D, terminalPositions map[lib.Point2D]bool) int64 {
+	current := topoMap[position.X][position.Y]
+	fmt.Printf("current: %v %v\n", current, position)
+	if current == '9' {
+		terminalPositions[position] = true
+		return 1
+	}
+
+	count := int64(0)
+	target := current + 1
+
+	if position.X > 0 && topoMap[position.X-1][position.Y] == target {
+		count += findTerminalPositions(topoMap, lib.Point2D{X: position.X - 1, Y: position.Y}, terminalPositions)
+	}
+
+	if position.X < int64(len(topoMap)-1) && topoMap[position.X+1][position.Y] == target {
+		count += findTerminalPositions(topoMap, lib.Point2D{X: position.X + 1, Y: position.Y}, terminalPositions)
+	}
+
+	if position.Y > 0 && topoMap[position.X][position.Y-1] == target {
+		count += findTerminalPositions(topoMap, lib.Point2D{X: position.X, Y: position.Y - 1}, terminalPositions)
+	}
+
+	if position.Y < int64(len(topoMap[0])-1) && topoMap[position.X][position.Y+1] == target {
+		count += findTerminalPositions(topoMap, lib.Point2D{X: position.X, Y: position.Y + 1}, terminalPositions)
+	}
+
+	return count
+}
+
+func parseMap(input string) ([][]rune, []lib.Point2D) {
+	var topoMap [][]rune
+	var trailHeads []lib.Point2D
+	for i, line := range lib.SplitLines(input) {
+		if len(line) == 0 {
+			continue
+		}
+
+		var row []rune
+		for j, char := range line {
+			row = append(row, char)
+
+			if char == '0' {
+				trailHeads = append(trailHeads, lib.Point2D{X: int64(i), Y: int64(j)})
+			}
+		}
+
+		topoMap = append(topoMap, row)
+	}
+
+	return topoMap, trailHeads
+}
+
+func main() {
+	name := os.Args[1]
+	content, err := lib.LoadFileContent(name)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	fmt.Printf("Part 1: %d\n", part1(content))
+	fmt.Printf("Part 2: %d\n", part2(content))
+}

2024/day10/main_test.go

@@ -0,0 +1,43 @@
+package main
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/kfarnung/advent-of-code/2024/lib"
+	"github.com/stretchr/testify/assert"
+)
+
+var input = strings.Join([]string{
+	"89010123",
+	"78121874",
+	"87430965",
+	"96549874",
+	"45678903",
+	"32019012",
+	"01329801",
+	"10456732",
+	"",
+}, "\n")
+
+func TestPart1(t *testing.T) {
+	assert.Equal(t, int64(36), part1(input))
+
+	inputContent, err := lib.GetInputContent()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	assert.Equal(t, int64(593), part1(inputContent))
+}
+
+func TestPart2(t *testing.T) {
+	assert.Equal(t, int64(81), part2(input))
+
+	inputContent, err := lib.GetInputContent()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	assert.Equal(t, int64(1192), part2(inputContent))
+}