public class Solution
extends Object
1139 - Largest 1-Bordered Square\.
Medium
Given a 2D `grid` of `0`s and `1`s, return the number of elements in the largest **square** subgrid that has all `1`s on its **border** , or `0` if such a subgrid doesn't exist in the `grid`.
**Example 1:**
**Input:** grid = \[\[1,1,1],[1,0,1],[1,1,1]]
**Output:** 9
**Example 2:**
**Input:** grid = \[\[1,1,0,0]]
**Output:** 1
**Constraints:**
* `1 <= grid.length <= 100`
* `1 <= grid[0].length <= 100`
* `grid[i][j]` is `0` or `1`