2021 Day 15 Complete!

2021/day15/main.go

@@ -0,0 +1,144 @@
+package main
+
+import (
+	"fmt"
+	"os"
+
+	h "git.bullercodeworks.com/brian/adventofcode/helpers"
+)
+
+var cave h.CoordByteMap
+var debug bool
+
+func main() {
+	debug = len(os.Args) > 1 && os.Args[1] == "--debug"
+	inp := h.StdinToStringSlice()
+	cave = h.StringSliceToCoordByteMap(inp)
+	fmt.Println("# Part 1")
+	part1()
+	fmt.Println("# Part 2")
+	part2()
+}
+
+var visited map[h.Coordinate]bool
+var distance map[h.Coordinate]int
+var curr h.Coordinate
+
+func part1() {
+	distance = make(map[h.Coordinate]int)
+	visited = make(map[h.Coordinate]bool)
+	for k := range cave.Field {
+		visited[k] = false
+		distance[k] = h.MAX_INT
+	}
+	curr = h.Coordinate{
+		X: 0,
+		Y: 0,
+	}
+	distance[curr] = 0
+	visited[curr] = true
+
+	work()
+	fmt.Println(distance[h.Coordinate{X: cave.Width - 1, Y: cave.Height - 1}])
+}
+
+func work() {
+	// Find the unvisited node with the smallest tentative distance
+	var c h.Coordinate
+	cDist := h.MAX_INT
+	for k, v := range distance {
+		if visited[k] {
+			continue
+		}
+		if v < cDist {
+			cDist = v
+			c = k
+		}
+	}
+
+	check := getNeighbors(c)
+	for _, v := range check {
+		if !visited[v] {
+			if b, ok := distance[v]; !ok || b > distance[c]+getInt(v) {
+				distance[v] = distance[c] + getInt(v)
+			}
+		}
+	}
+	visited[c] = true
+
+	// if we still have unvisited nodes, recurse
+	if moreWork() {
+		work()
+	}
+}
+
+func moreWork() bool {
+	for i := range visited {
+		if visited[i] == false {
+			return true
+		}
+	}
+	return false
+}
+
+func part2() {
+	// Build the full cave
+	expandCave(5)
+	part1()
+}
+
+func getInt(c h.Coordinate) int {
+	return int(cave.Opt(c, '0')) - int('0')
+}
+
+func getNeighbors(c h.Coordinate) []h.Coordinate {
+	var ret []h.Coordinate
+	for _, n := range []h.Coordinate{c.North(), c.East(), c.South(), c.West()} {
+		if v := cave.Opt(n, 'Z'); v != 'Z' {
+			ret = append(ret, n)
+		}
+	}
+	return ret
+}
+
+func expandCave(size int) {
+	oH, oW := cave.Height, cave.Width
+	for i := 1; i < size; i++ {
+		for y := 0; y < oH; y++ {
+			for x := 0; x < oW; x++ {
+				ny := (oH*i + y)
+				prev := h.Coordinate{
+					X: x,
+					Y: (oH*(i-1) + y),
+				}
+				pv := cave.Get(prev)
+				var v byte
+				if pv == '9' {
+					v = '1'
+				} else {
+					v = pv + 1
+				}
+				cave.Put(h.Coordinate{X: x, Y: ny}, v)
+			}
+		}
+	}
+	for y := 0; y < cave.Height; y++ {
+		for i := 1; i < size; i++ {
+			for x := 0; x < oW; x++ {
+				nx := (oW*i + x)
+				prev := h.Coordinate{
+					X: (oW*(i-1) + x),
+					Y: y,
+				}
+				pv := cave.Get(prev)
+				var v byte
+				if pv == '9' {
+					v = '1'
+				} else {
+					v = pv + 1
+				}
+				cave.Put(h.Coordinate{X: nx, Y: y}, v)
+			}
+		}
+	}
+}