public class Solution
extends Object
1536 - Minimum Swaps to Arrange a Binary Grid\.
Medium
Given an `n x n` binary `grid`, in one step you can choose two **adjacent rows** of the grid and swap them.
A grid is said to be **valid** if all the cells above the main diagonal are **zeros**.
Return _the minimum number of steps_ needed to make the grid valid, or **\-1** if the grid cannot be valid.
The main diagonal of a grid is the diagonal that starts at cell `(1, 1)` and ends at cell `(n, n)`.
**Example 1:**
**Input:** grid = \[\[0,0,1],[1,1,0],[1,0,0]]
**Output:** 3
**Example 2:**
**Input:** grid = \[\[0,1,1,0],[0,1,1,0],[0,1,1,0],[0,1,1,0]]
**Output:** -1
**Explanation:** All rows are similar, swaps have no effect on the grid.
**Example 3:**
**Input:** grid = \[\[1,0,0],[1,1,0],[1,1,1]]
**Output:** 0
**Constraints:**
* `n == grid.length` `== grid[i].length`
* `1 <= n <= 200`
* `grid[i][j]` is either `0` or `1`