You are given an n $ imes$ n binary matrix grid. In a single operation, you can choose any two adjacent rows and swap them.

The grid is considered valid if all cells situated strictly above the main diagonal are $0$.

Return the minimum number of operations needed to make grid valid, or $-1$ if it is impossible to make it valid.

Note: The main diagonal consists of the cells grid[i][j] where i $=$ j. Cells strictly above the main diagonal are those where i $<$ j.

Constraints:

• n $=$ grid.length $=$ grid[i].length

• $1 \leq$ n $\leq 200$

• grid[i][j] is either $0$ or $1$

Now, let’s take a moment to make sure you’ve correctly understood the problem. The quiz below helps you check if you’re solving the correct problem:

We have a game for you to play. Rearrange the logical building blocks to develop a clearer understanding of how to solve this problem.

Implement your solution in the following coding playground.