day06_part01.fs

module day06_part01

open AdventOfCode_2024.Modules

type Direction =
    | UP
    | DOWN
    | RIGHT
    | LEFT

type MapDefinition = {
    Definition : char [,]
    PatrolPos: int array;
    PatrolDirection : Direction
    Blockers: int array list
}

let getDir(dir: Direction) =
    match dir with
    | UP -> [| -1; 0 |]
    | DOWN -> [| 1; 0 |]
    | RIGHT -> [| 0; 1 |]
    | LEFT -> [| 0; -1 |]

let turnRight(dir: Direction) =
    match dir with
    | UP -> RIGHT
    | DOWN -> LEFT
    | RIGHT -> DOWN
    | LEFT -> UP

let parseContent(lines: string array) =
    let map = Array2D.create lines.Length lines[0].Length '.'
    let patrolPos = [|0; 0|]

    let blockers =
        [for rIdx in 0..lines.Length-1 do
                for cIdx in 0..lines[rIdx].Length-1 do
                    let value = lines[rIdx][cIdx]
                    if value = '^' then
                        patrolPos[0] <- rIdx
                        patrolPos[1] <- cIdx
                    if value = '#' then
                        yield [|rIdx; cIdx|]
                    map[rIdx, cIdx] <- lines[rIdx][cIdx]
        ]
    { Definition = map; PatrolPos = patrolPos; PatrolDirection = UP; Blockers = blockers }

let printMap (map: char[,]) =
    for row in [0..map.GetUpperBound(0)] do
        for column in [0..map.GetUpperBound(1) ] do
            printf "%c" map[row, column]
        printfn ""

let outOfBoundaries(row: int) (col: int) (maxRows: int) (maxCols: int) =
    row >= 0 && row < maxRows && col >= 0 && col < maxCols

let patrol(patrol: MapDefinition) =
    let mutable outOfRange = false
    let mutable currentDirection = patrol.PatrolDirection

    let pos = [|patrol.PatrolPos[0]; patrol.PatrolPos[1]|]
    
    let maxRows = patrol.Definition.GetLength(0)
    let maxCols = patrol.Definition.GetLength(1)

    let visitedMap = Array2D.create maxRows maxCols '.'
    visitedMap[pos[0], pos[1]] <- 'X'

    let visited = 
        [visitedMap[pos[0], pos[1]]] @
        [while not outOfRange do
            let currentDir = getDir currentDirection
            pos[0] <- pos[0] + currentDir[0]
            pos[1] <- pos[1] + currentDir[1]
            if not (outOfBoundaries pos[0] pos[1] maxRows maxCols) then
                outOfRange <- true
            else
                let mapvalue = patrol.Definition[pos[0], pos[1]]
                if mapvalue <> '#' then
                    if visitedMap[pos[0], pos[1]] <> 'X' then
                        visitedMap[pos[0], pos[1]] <- 'X'
                        yield visitedMap[pos[0], pos[1]]
                else
                    pos[0] <- pos[0] - currentDir[0]
                    pos[1] <- pos[1] - currentDir[1]
                    currentDirection <- turnRight currentDirection]
    (visitedMap, visited.Length)

let execute() =
    let path = "day06/day06_input.txt"
    let content = LocalHelper.GetLinesFromFile path
    let mapDefinition = parseContent content
    let (visited, counted) = patrol mapDefinition
    counted