Solution for 2024, day 10

Author: lucianoq

2024/10/Makefile

@@ -0,0 +1,19 @@
+input:
+	http "https://adventofcode.com/2024/day/10/input" "Cookie:session=${AOC_SESSION};" >input
+
+main1:
+	go build -o main1 main1.go common.go
+
+main2:
+	go build -o main2 main2.go common.go
+
+.PHONY: run1 run2 clean
+
+run1: main1 input
+	./main1 <input
+
+run2: main2 input
+	./main2 <input
+
+clean:
+	rm -f main1 main2 input

2024/10/common.go

@@ -0,0 +1,52 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+)
+
+const Size = 60
+
+type P struct{ x, y int }
+
+func (p P) Neighbors() []P {
+	return []P{
+		{p.x - 1, p.y}, //N
+		{p.x + 1, p.y}, //S
+		{p.x, p.y - 1}, //W
+		{p.x, p.y + 1}, //E
+	}
+}
+
+func inMap(p P) bool {
+	return p.x >= 0 && p.x < Size && p.y >= 0 && p.y < Size
+}
+
+func main() {
+	h := parseMap()
+
+	sum := 0
+	for i := 0; i < Size; i++ {
+		for j := 0; j < Size; j++ {
+			if h[P{i, j}] == 0 {
+				sum += score(h, P{i, j})
+			}
+		}
+	}
+
+	fmt.Println(sum)
+}
+
+func parseMap() map[P]uint8 {
+	scanner := bufio.NewScanner(os.Stdin)
+
+	h := map[P]uint8{}
+	for i := 0; scanner.Scan(); i++ {
+		line := scanner.Text()
+		for j := 0; j < len(line); j++ {
+			h[P{i, j}] = line[j] - '0'
+		}
+	}
+	return h
+}

2024/10/main1.go

@@ -0,0 +1,23 @@
+package main
+
+// find peaks
+func score(h map[P]uint8, p P) int {
+	peaks := map[P]struct{}{}
+	findPeaksRecursive(h, p, peaks)
+	return len(peaks)
+}
+
+func findPeaksRecursive(h map[P]uint8, p P, peaks map[P]struct{}) {
+	if h[p] == 9 {
+		peaks[p] = struct{}{}
+		return
+	}
+
+	for _, adj := range p.Neighbors() {
+		if inMap(adj) {
+			if h[adj] == h[p]+1 {
+				findPeaksRecursive(h, adj, peaks)
+			}
+		}
+	}
+}

2024/10/main2.go

@@ -0,0 +1,18 @@
+package main
+
+// find paths
+func score(h map[P]uint8, p P) int {
+	if h[p] == 9 {
+		return 1
+	}
+
+	paths := 0
+	for _, adj := range p.Neighbors() {
+		if inMap(adj) {
+			if h[adj] == h[p]+1 {
+				paths += score(h, adj)
+			}
+		}
+	}
+	return paths
+}