2022 Day 24 Complete

2022/day24/main.go

@@ -0,0 +1,121 @@
+package main
+
+import (
+	"fmt"
+	"strings"
+
+	h "git.bullercodeworks.com/brian/adventofcode/helpers"
+)
+
+func main() {
+	input := h.StdinToStringSlice()
+	part1(input)
+	part2(input)
+}
+
+func part1(input []string) {
+	field, blizzards, start, target := parseInput(input)
+	fmt.Println("# Part 1")
+	fmt.Println(run(field, blizzards, start, target))
+}
+
+func part2(input []string) {
+	field, blizzards, start, target := parseInput(input)
+	fmt.Println("# Part 2")
+	fmt.Println(run(field, blizzards, start, target) +
+		run(field, blizzards, target, start) +
+		run(field, blizzards, start, target))
+}
+
+type Blizzard struct {
+	pos, dir, wrap h.Coordinate
+}
+
+var (
+	U = h.Coordinate{X: 0, Y: -1}
+	D = h.Coordinate{X: 0, Y: 1}
+	L = h.Coordinate{X: -1, Y: 0}
+	R = h.Coordinate{X: 1, Y: 0}
+)
+
+var directions []h.Coordinate = []h.Coordinate{U, D, L, R}
+
+func parseInput(lines []string) (field [][]rune, blizzards []Blizzard, start, target h.Coordinate) {
+	start.X = strings.Index(lines[0], "E")
+	if start.X == -1 {
+		start.X = strings.Index(lines[0], ".")
+	}
+	target.Y = len(lines) - 1
+	target.X = strings.Index(lines[target.Y], ".")
+	for _, line := range lines {
+		line = strings.TrimSpace(line)
+		field = append(field, []rune(line))
+	}
+	for y, row := range field {
+		for x, c := range row {
+			switch c {
+			case '^':
+				blizzards = append(blizzards, Blizzard{
+					h.Coordinate{X: x, Y: y}, U, h.Coordinate{X: x, Y: len(field) - 2},
+				})
+			case 'v':
+				blizzards = append(blizzards, Blizzard{
+					h.Coordinate{X: x, Y: y}, D, h.Coordinate{X: x, Y: 1},
+				})
+			case '<':
+				blizzards = append(blizzards, Blizzard{
+					h.Coordinate{X: x, Y: y}, L, h.Coordinate{X: len(field[0]) - 2, Y: y},
+				})
+			case '>':
+				blizzards = append(blizzards, Blizzard{
+					h.Coordinate{X: x, Y: y}, R, h.Coordinate{X: 1, Y: y},
+				})
+			}
+		}
+	}
+	return
+}
+
+func valid(field [][]rune, pos h.Coordinate) bool {
+	return pos.X >= 0 && pos.X < len(field[0]) && pos.Y >= 0 && pos.Y < len(field)
+}
+
+func run(field [][]rune, blizzards []Blizzard, start, target h.Coordinate) int {
+	minutes := 0
+	currentStep := make(map[h.Coordinate]bool)
+	currentStep[start] = true
+
+	for !currentStep[target] {
+		//update blizzards
+		whereBlizzards := make(map[h.Coordinate]bool)
+		for i, b := range blizzards {
+			bb := b.pos.Add(b.dir)
+			if valid(field, bb) {
+				if field[bb.Y][bb.X] == '#' {
+					blizzards[i].pos = b.wrap
+				} else {
+					blizzards[i].pos = bb
+				}
+			}
+			whereBlizzards[blizzards[i].pos] = true
+		}
+
+		//find new steps
+		newStep := make(map[h.Coordinate]bool)
+		for pos := range currentStep {
+			if !(whereBlizzards[pos]) {
+				newStep[pos] = true
+			}
+			for _, d := range directions {
+				n := pos.Add(d)
+				if valid(field, n) && field[n.Y][n.X] != '#' && !whereBlizzards[n] {
+					newStep[n] = true
+				}
+			}
+		}
+		currentStep = newStep
+		minutes++
+	}
+
+	return minutes
+}