URL
Spiral Matrix III - LeetCode
Code
https://github.com/syohex/dotnet-study/tree/master/fsharp/leetcode/challenge/202408/spiral_matrix_3/main.fsx
let spiralMatrixIII (rows: int) (cols: int) (rStart: int) (cStart: int) : (int * int) list =
let steps = [| (0, 1); (1, 0); (0, -1); (-1, 0) |]
let limit = rows * cols
let rec spiralMatrixIII' row col direction step acc =
if List.length acc >= limit then
List.rev acc
else
let (acc, row, col, direction) =
seq { 1..2 }
|> Seq.fold
(fun (acc, row, col, direction) _ ->
let (acc, row, col) =
seq { 0 .. (step - 1) }
|> Seq.fold
(fun (acc, row, col) _ ->
let x, y = steps.[direction]
if row >= 0 && row < rows && col >= 0 && col < cols then
(row, col) :: acc, row + x, col + y
else
acc, row + x, col + y)
(acc, row, col)
acc, row, col, (direction + 1) % 4)
(acc, row, col, direction)
spiralMatrixIII' row col direction (step + 1) acc
spiralMatrixIII' rStart cStart 0 1 []
