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|
package main
import (
"container/heap"
"fmt"
"os"
"strings"
)
func FileRead(path string) string {
file, err := os.ReadFile(path)
if err != nil {
fmt.Println("Couldn't Read file: ", err)
}
return string(file)
}
type Grid = [][]byte
type Point struct {
x int
y int
}
func parseInput(data string) Grid {
lines := strings.Split(data, "\n")
var grid Grid
for _, line := range lines {
if len(line) > 0 {
bytes := []byte(line)
grid = append(grid, bytes)
}
}
return grid
}
func printGrid(grid [][]byte) {
for _, row := range grid {
for _, cell := range row {
fmt.Printf(string(cell))
}
fmt.Println()
}
}
func copySlice(src []Point) []Point {
dest := make([]Point, len(src))
copy(dest, src)
return dest
}
func findMin(arr []int) int {
min := arr[0]
for _, v := range arr[1:] {
if v < min {
min = v
}
}
return min
}
type Direction struct {
dx, dy int
}
type State struct {
cost int
stepCount int
pos Point
dir Direction
}
type PriorityQueue []*State
func (pq PriorityQueue) Len() int { return len(pq) }
func (pq PriorityQueue) Less(i, j int) bool {
return pq[i].cost < pq[j].cost
}
func (pq PriorityQueue) Swap(i, j int) {
pq[i], pq[j] = pq[j], pq[i]
}
func (pq *PriorityQueue) Push(x interface{}) {
item := x.(*State)
*pq = append(*pq, item)
}
func (pq *PriorityQueue) Pop() interface{} {
old := *pq
n := len(old)
item := old[n-1]
*pq = old[0 : n-1]
return item
}
func inBounds(x, y, rows, cols int, grid [][]byte) bool {
return x >= 0 && x < rows && y >= 0 && y < cols && grid[x][y] != '#'
}
func findPosition(grid [][]byte, target byte) (Point, bool) {
for i := range grid {
for j := range grid[i] {
if grid[i][j] == target {
return Point{i, j}, true
}
}
}
return Point{}, false
}
func dijkstra(grid [][]byte, start Point, end Point) (int, int, []Point) { // Returns cost, step count, and path
if start == end {
return 0, 0, []Point{start}
}
var directions = [4]Direction{
{1, 0}, // Down
{0, 1}, // Right
{-1, 0}, // Up
{0, -1}, // Left
}
pq := &PriorityQueue{}
heap.Init(pq)
type Key struct {
x, y, dx, dy int
}
minCost := make(map[Key]int)
stepCounts := make(map[Key]int)
prev := make(map[Key]Key) // Track previous position for path reconstruction
prevDir := make(map[Key]Direction) // Track previous direction
heap.Push(pq, &State{cost: 0, stepCount: 0, pos: start, dir: Direction{0, 0}})
for pq.Len() > 0 {
current := heap.Pop(pq).(*State)
cost := current.cost
stepCount := current.stepCount
pos := current.pos
dir := current.dir
key := Key{pos.x, pos.y, dir.dx, dir.dy}
if existingCost, exists := minCost[key]; exists && cost >= existingCost {
continue
}
minCost[key] = cost
stepCounts[key] = stepCount
if pos == end {
// Reconstruct path
path := []Point{end}
currentKey := key
for currentKey.x != start.x || currentKey.y != start.y {
previousKey := prev[currentKey]
path = append([]Point{{previousKey.x, previousKey.y}}, path...)
currentKey = previousKey
}
return cost, stepCount, path
}
for _, d := range directions {
nx, ny := pos.x+d.dx, pos.y+d.dy
if inBounds(nx, ny, len(grid), len(grid[0]), grid) {
var newCost int
if dir == (Direction{0, 0}) || d == dir {
newCost = cost + 1
} else {
newCost = cost + 1001
}
newStepCount := stepCount + 1
newKey := Key{nx, ny, d.dx, d.dy}
if existingCost, exists := minCost[newKey]; !exists || newCost < existingCost {
heap.Push(pq, &State{cost: newCost, stepCount: newStepCount, pos: Point{nx, ny}, dir: d})
prev[newKey] = key // Store the previous position
prevDir[newKey] = dir // Store the previous direction
}
}
}
}
return 0, 0, nil // 'S' is not reachable
}
func solve_part_one(data string) int {
maze := parseInput(data)
start, _ := findPosition(maze, 'E')
end, _ := findPosition(maze, 'S')
cost, _, _ := dijkstra(maze, start, end)
return cost
}
func solve_part_two(data string) int {
maze := parseInput(data)
start, _ := findPosition(maze, 'E')
end, _ := findPosition(maze, 'S')
bestCost, _, path := dijkstra(maze, start, end)
uniquePoints := make(map[Point]struct{})
for _, p := range path {
uniquePoints[p] = struct{}{}
}
fmt.Println(bestCost)
for i := range maze {
for j := range maze[i] {
currentPoint := Point{i, j}
_, exists := uniquePoints[currentPoint]
if exists {
continue
}
costCurToStart, _, pathStart := dijkstra(maze, start, currentPoint)
costCurToEnd, _, pathEnd := dijkstra(maze, currentPoint, end)
if costCurToStart+costCurToEnd+1000 == bestCost || costCurToStart+costCurToEnd == bestCost {
for _, p := range pathStart {
uniquePoints[p] = struct{}{}
}
for _, p := range pathEnd {
uniquePoints[
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