You are a hiker preparing for an upcoming hike. You are given `heights`, a 2D array of size `rows x columns`, where `heights[row][col]` represents the height of cell `(row, col)`. You are situated in the top-left cell, `(0, 0)`, and you hope to travel to the bottom-right cell, `(rows-1, columns-1)` (i.e., 0-indexed). You can move up, down, left, or right, and you wish to find a route that requires the minimum effort.

A route's effort is the maximum absolute difference in heights between two consecutive cells of the route.

Return the minimum effort required to travel from the top-left cell to the bottom-right cell.

Example 1:

    Input: heights = [[1,2,2],[3,8,2],[5,3,5]]

    Output: 2

    Explanation: The route of [1,3,5,3,5] has a maximum absolute difference of 2 in consecutive cells.

    This is better than the route of [1,2,2,2,5], where the maximum absolute difference is 3.

Example 2:

    Input: heights = [[1,2,3],[3,8,4],[5,3,5]]

    Output: 1

    Explanation: The route of [1,2,3,4,5] has a maximum absolute difference of 1 in consecutive cells, which is better than route [1,3,5,3,5].

Example 3:

    Input: heights = [[1,2,1,1,1],[1,2,1,2,1],[1,2,1,2,1],[1,2,1,2,1],[1,1,1,2,1]]

    Output: 0

    Explanation: This route does not require any effort.

Constraints:

- `rows == heights.length`
- `columns == heights[i].length`
- `1 <= rows, columns <= 100`
- `1 <= heights[i][j] <= 106`