2024 day 18 Complete

2024/day18/main.go

@@ -0,0 +1,113 @@
+package main
+
+import (
+	"fmt"
+
+	h "git.bullercodeworks.com/brian/adventofcode/helpers"
+)
+
+func main() {
+	inp := h.StdinToStringSlice()
+	// size, bytes := 6, 12 // Test Input
+	size, bytes := 70, 1024 // Actual Input
+	part1(inp, size, bytes)
+	fmt.Println()
+	part2(inp, size, bytes)
+}
+
+func part1(inp []string, size, bytes int) {
+	// bytes:= 12 // Test Input
+	m := h.NewCoordByteMap()
+	m.BRX, m.BRY = size, size
+	drops := parseInput(inp)
+	for i := 0; i < bytes; i++ {
+		m.Put(drops[i], '#')
+	}
+
+	fmt.Println("# Part 1")
+	fmt.Println(FindShortestPath(m, func(a, b State) bool {
+		return a.cnt+a.dist < b.cnt+b.dist
+	}))
+}
+
+func part2(inp []string, size, bytes int) {
+	m := h.NewCoordByteMap()
+	m.BRX, m.BRY = size, size
+	drops := parseInput(inp)
+	// We can skip up to 'bytes', part1 showed that that many work
+	for i := 0; i < bytes; i++ {
+		m.Put(drops[i], '#')
+	}
+
+	fmt.Println("# Part 2")
+	for tm, b := range drops[bytes+1:] {
+		m.Put(b, '#')
+		if FindShortestPath(m, func(a, b State) bool {
+			return a.dist < b.dist
+		}) == -1 {
+			fmt.Printf("Blocked at %d: %s\n", bytes+tm, b.String())
+			return
+		}
+	}
+}
+
+func parseInput(inp []string) []h.Coordinate {
+	var ret []h.Coordinate
+	for i := range inp {
+		c := h.Coordinate{}
+		fmt.Sscanf(inp[i], "%d,%d", &c.X, &c.Y)
+		ret = append(ret, c)
+	}
+	return ret
+}
+
+type State struct {
+	c    h.Coordinate
+	cnt  int
+	dist int
+}
+
+func FindShortestPath(inp h.CoordByteMap, less func(a, b State) bool) int {
+	visited := make(map[h.Coordinate]State)
+	end := h.Coordinate{X: inp.BRX, Y: inp.BRY}
+	start := h.Coordinate{X: 0, Y: 0}
+	startState := State{
+		c:    start,
+		cnt:  0,
+		dist: start.Distance(end),
+	}
+	queue := h.NewHeap[State](less)
+	queue.Push(startState)
+
+	for queue.Len() > 0 {
+		step := queue.Pop()
+		if step.c.Equals(end) {
+			visited[end] = step
+			break
+		}
+
+		if _, ok := visited[step.c]; ok {
+			continue
+		}
+		visited[step.c] = step
+		// Find next steps
+		for _, n := range step.c.GetOrthNeighbors() {
+			if !inp.ContainsCoord(n) || inp.Get(n) == '#' {
+				continue
+			}
+			if _, ok := visited[n]; ok {
+				continue
+			}
+			nState := State{
+				c:    n,
+				cnt:  step.cnt + 1,
+				dist: n.Distance(end),
+			}
+			queue.Push(nState)
+		}
+	}
+	if v, ok := visited[end]; ok {
+		return v.cnt
+	}
+	return -1
+}

2024/day18/testinput

@@ -0,0 +1,25 @@
+5,4
+4,2
+4,5
+3,0
+2,1
+6,3
+2,4
+1,5
+0,6
+3,3
+2,6
+5,1
+1,2
+5,5
+2,5
+6,5
+1,4
+0,4
+6,4
+1,1
+6,1
+1,0
+0,5
+1,6
+2,0