input: Write a function to solve a maze using an object-oriented structure in Python. The maze is represented by a 2D grid where '1' indicates a path and '0' indicates a wall. The function should find a path from the top-left corner to the bottom-right corner and return the number of steps taken to reach the end. If no path is found, the function should return an empty list.
  
  class Maze:
      def __init__(self, n, m):
          self._n, self._m = n, m
          self._grid = [[None] * m for _ in range(n)]
  
      def solve_maze(self):
          result, found = [], False
          start, end = (0, 0), (self._n-1, self._m-1)
  
          for i in range(self._n):
              for j in range(self._m):
                  if self._grid[i][j] == 1:
                      value = 0
                      self._find_omega(i, j, value, result, start, end,
                                       found)
                      return result
  
      def _find_omega(self, i, j, value,
                      result, start, end, found):
          rowNbr, colNbr = [-1, 0, 0, 1], [0, -1, 1, 0]
  
          if (i, j) == end:
              found = True
              result.append(value)
              return
  
          if found == True:
              return
  
          self._grid[i][j] = 0
          for k in range(4):
              if self._on_board(i + rowNbr[k], j + colNbr[k]):
                  self._find_omega(i + rowNbr[k], j + colNbr[k],
                                   value + 1, result,
                                   start, end, found)
  
      def _on_board(self, i, j):
          return 0 <= i < self._n and 0 <= j < self._m and self._grid[i][j] == 1
  
  assert Maze(3, 3)._grid = [[1, 0, 1], [1, 1, 0], [0, 1, 1]]
  assert Maze(3, 3).solve_maze() == [4]
  
  assert Maze(2, 2)._grid = [[1, 0], [1, 1]]
  assert Maze(2, 2).solve_maze() == [2]
  
  assert Maze(2, 2)._grid = [[1, 0], [0, 1]]
  assert Maze(2, 2).solve_maze() == []
  
  assert Maze(1, 1)._grid = [[1]]
  assert Maze(1, 1).solve_maze() == [0]
output: def solve_maze(self):
      result, found = [], False
      start, end = (0, 0), (self._n-1, self._m-1)
      queue = [(start, 0)]
      visited = set()
  
      while queue:
          (i, j), value = queue.pop(0)
  
          if (i, j) == end:
              result.append(value)
              return result
  
          if (i, j) in visited:
              continue
  
          visited.add((i, j))
  
          for k in range(4):
              ni, nj = i + [-1, 0, 0, 1][k], j + [0, -1, 1, 0][k]
              if self._on_board(ni, nj):
                  queue.append(((ni, nj), value + 1))
  
      return []