adventofcode2025/6/main.go

package main

import (
	"bufio"
	"fmt"
	"os"
	"strings"
)

func findPosition(layout [][]string) []int {
  position := []int{}
  for i := range layout {
    for j := range layout[i] {
      if layout[i][j] == "^" {
        position = append(position, i, j)
      }
    }
  }
  return position
}

func findObstacles(layout [][]string) [][]int {
  positions := [][]int{}
  for i := range layout {
    for j := range layout[i] {
      if layout[i][j] == "#" {
        positions = append(positions, []int{i,j})
      }
    }
  }
  return positions
}

func calcPath(layout [][]string) ([][]int, bool) {
  circle := false
  direction := "up"
  guardPosition:=findPosition(layout)
  inBound := true
  currentPosition := guardPosition
  path := [][]int{currentPosition}
  for inBound && !circle {
    if direction == "up" {
      if currentPosition[0] == 0 {
        inBound = false
        break
      } else if layout[currentPosition[0]-1][currentPosition[1]] == "#" {
        direction = "right"
        continue
      } else {
        currentPosition = []int{currentPosition[0]-1, currentPosition[1]}
        if checkCircle(path, currentPosition) {
          circle = true
        } else {
          path = append(path, currentPosition)
        }
      }
    }
    if direction == "right" {
      if currentPosition[1] == len(layout)-1 {
        inBound = false
        break
      } else if layout[currentPosition[0]][currentPosition[1]+1] == "#" {
        direction = "down"
        continue
      } else {
        currentPosition = []int{currentPosition[0], currentPosition[1]+1}
        if checkCircle(path, currentPosition) {
          circle = true
        } else {
          path = append(path, currentPosition)
        }
      }
    }
    if direction == "down" {
      if currentPosition[0] == len(layout)-1 {
        inBound = false
        break
      } else if layout[currentPosition[0]+1][currentPosition[1]] == "#" {
        direction = "left"
        continue
      } else {
        currentPosition = []int{currentPosition[0]+1, currentPosition[1]}
        if checkCircle(path, currentPosition) {
          circle = true
        } else {
          path = append(path, currentPosition)
        }
      }
    }
    if direction == "left" {
      if currentPosition[1] == 0 {
        inBound = false
        break
      } else if layout[currentPosition[0]][currentPosition[1]-1] == "#" {
        direction = "up"
        continue
      } else {
        currentPosition = []int{currentPosition[0], currentPosition[1]-1}
        if checkCircle(path, currentPosition) {
          circle = true
        } else {
          path = append(path, currentPosition)
        }
      }
    }
  }
  return path, circle
}

func checkCircle(path [][]int, position []int) bool {
  result := false
  for i:=1;i<len(path);i++  {
    if path[i][0] == position[0] && path[i][1] == position[1] {
      if i < len(path)-1 && path[i-1][0] == path[len(path)-1][0] && path[i-1][1] == path[len(path)-1][1] {
        result = true
      }
    }
  }
  return result
}

func main() {
  file, _ := os.Open("input")
  defer file.Close()
  scanner := bufio.NewScanner(file)
  layout := [][]string{}
  for scanner.Scan() {
    line := scanner.Text()
    layout = append(layout, strings.Split(line, ""))
  }
//  fmt.Println(path)
//  fmt.Println(len(path))
  path, _ := calcPath(layout)
  pathOccurances := make(map[[2]int]int)
  for _, tuple := range path {
    key := [2]int{tuple[0],tuple[1]}
    pathOccurances[key]++
  }
  fmt.Println(len(pathOccurances))
  circleSpots := [][]int{}
  for i:=1;i<len(path);i++ {
    if path[i][0] == path[0][0] && path[i][1] == path[0][1] {
      continue
    } else {
      tempValue := layout[path[i][0]][path[i][1]]
      layout[path[i][0]][path[i][1]] = "#"
      _, circle := calcPath(layout)
      if circle {
        circleSpots = append(circleSpots, path[i])
      }
      layout[path[i][0]][path[i][1]] = tempValue
    }
  }
  uniqueCircles := make(map[[2]int]int)
  for _, tuple := range circleSpots {
    key := [2]int{tuple[0],tuple[1]}
    uniqueCircles[key]++
  }
  fmt.Println(len(uniqueCircles))
}