Find minimum threshold enabling grid path

## Problem You are given an `m x n` integer grid `grid`. You start at the top-left cell `(0, 0)` and want to reach the bottom-right cell `(m-1, n-1)`. You may move **one step** at a time in **4 directions**: up, down, left, right (no diagonals). You may not go outside the grid. Define a threshold value `T`. A path is **valid under threshold `T`** if **every cell value on the path is `<= T`**. ### Task Return the **minimum integer `T`** such that there exists **at least one** valid path from `(0,0)` to `(m-1,n-1)` under threshold `T`. ### Input - `grid`: a 2D array of integers with dimensions `m x n`. ### Output - An integer: the minimum `T` that makes the destination reachable. ### Notes / Constraints (assume) - `1 <= m, n <= 200` - Cell values are integers (may be large; e.g., up to `10^9` in absolute value). - Movement is 4-directional. ### Example If `grid = [[0,2],[1,3]]`, the answer is `3` because you cannot reach the bottom-right without allowing the cell value `3`.