Regions Cut By Slashes

export function regionsBySlashes(grid: string[]): number {
  const n = grid.length;
  const board: number[][] = Array.from({ length: 3 * n }, () => new Array(3 * n).fill(0));
  for (let i = 0; i < n; i++) {
    for (let j = 0; j < n; j++) {
      if (grid[i][j] === '/' || grid[i][j] === '\\') {
        cutBySlash(board, grid[i][j], i * 3, j * 3);
      }
    }
  }
 
  let answer = 0;
  for (let y = 0; y < n * 3; y++) {
    for (let x = 0; x < n * 3; x++) {
      if (findRegion(board, y, x)) {
        answer += 1;
      }
    }
  }
  return answer;
}
 
function cutBySlash(board: number[][], slash: string, y: number, x: number) {
  let [cy, cx] = slash === '/' ? [y, x + 2] : [y, x];
  const [dy, dx] = slash === '/' ? [1, -1] : [1, 1];
  for (let i = 0; i < 3; i++) {
    board[cy][cx] = 1;
    [cy, cx] = [cy + dy, cx + dx];
  }
}
 
function findRegion(board: number[][], y: number, x: number) {
  if (Math.min(y, x) < 0 || Math.max(y, x) >= board.length || board[y][x] === 1) {
    return false;
  }
  board[y][x] = 1;
  const directions = [
    [-1, 0],
    [1, 0],
    [0, -1],
    [0, 1],
  ];
  for (const [dy, dx] of directions) {
    findRegion(board, y + dy, x + dx);
  }
  return true;
}