2024 Day 20 Complete!

2024/day20/main.go

@@ -0,0 +1,53 @@
+package main
+
+import (
+	"fmt"
+
+	h "git.bullercodeworks.com/brian/adventofcode/helpers"
+)
+
+func main() {
+	inp := h.StdinToStringSlice()
+	solve(inp)
+}
+
+var (
+	N    = h.Coordinate{X: 0, Y: -1}
+	E    = h.Coordinate{X: 1, Y: 0}
+	S    = h.Coordinate{X: 0, Y: 1}
+	W    = h.Coordinate{X: -1, Y: 0}
+	Dirs = []h.Coordinate{N, E, S, W}
+)
+
+func solve(inp []string) {
+	m := h.StringSliceToCoordByteMap(inp)
+	start, _ := m.FindFirst('S')
+	// Find the path through the map
+	queue, dist := []h.Coordinate{start}, map[h.Coordinate]int{start: 0}
+	for len(queue) > 0 {
+		p := queue[0]
+		queue = queue[1:]
+		for _, d := range Dirs {
+			n := p.Add(d)
+			if _, ok := dist[n]; !ok && m.Get(n) != '#' {
+				queue, dist[n] = append(queue, n), dist[p]+1
+			}
+		}
+	}
+	part1, part2 := 0, 0
+	for p1 := range dist {
+		for p2 := range dist {
+			d := p1.Distance(p2)
+			if d <= 20 && dist[p2] >= dist[p1]+d+100 {
+				if d <= 2 {
+					part1++
+				}
+				part2++
+			}
+		}
+	}
+	fmt.Println("# Part 1")
+	fmt.Println(part1)
+	fmt.Println("\n# Part 2")
+	fmt.Println(part2)
+}