3797. Count Routes to Climb a Rectangular Grid

You are given a string array grid of size n, where each string grid[i] has length m. The character grid[i][j] is one of the following symbols: - '.': The cell is available. - '#': The cell is blocked. You want to count the number of different routes to climb grid. Each route must start from any cell in the bottom row (row n - 1) and end in the top row (row 0). However, there are some constrain