# LeetCode 1091. Shortest Path in Binary Matrix in F#

Shohei Yoshida
·May 16, 2022·

## URL

leetcode.com/problems/shortest-path-in-bina..

## Code

github.com/syohex/dotnet-study/blob/master/..

``````#r "nuget:FSharpx.Collections"

open FSharpx.Collections

let shortestPathBinaryMatrix (grid: int [,]) : int =
let steps =
[ (-1, -1)
(-1, 0)
(-1, 1)
(0, -1)
(0, 1)
(1, -1)
(1, 0)
(1, 1) ]

let rows = Array2D.length1 grid
let cols = Array2D.length2 grid

let rec shortestPathBinaryMatrix' (q: Queue<(int * int)>) (grid: int [,]) =
match Queue.tryUncons q with
| None -> -1
| Some ((x, y), rest) ->
if x = rows - 1 && y = cols - 1 then
grid.[x, y]
else
let q' =
steps
|> List.fold
(fun acc (xStep, yStep) ->
let row = x + xStep
let col = y + yStep

if row >= 0
&& row < rows
&& col >= 0
&& col < cols
&& grid.[row, col] = 0 then
grid.[row, col] <- grid.[x, y] + 1
Queue.conj (row, col) acc
else
acc)
rest

shortestPathBinaryMatrix' q' grid

if grid.[0, 0] = 1 then
-1
else
grid.[0, 0] <- 1
let q = Queue.empty |> Queue.conj (0, 0)
shortestPathBinaryMatrix' q grid
``````