1536. Minimum Swaps to Arrange a Binary Grid

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: