1536. Minimum Swaps to Arrange a Binary Grid

https://leetcode.com/problems/minimum-swaps-to-arrange-a-binary-grid

Description

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

• n == grid[i].length

• 1 <= n <= 200

• grid[i][j] is 0 or 1

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