Minimum Adjacent Row Swaps for Zeros Above the Diagonal
Company: Amazon
Role: Software Engineer
Category: Coding & Algorithms
Difficulty: medium
Interview Round: Other
### Problem
You may swap only neighboring rows of the square binary grid. A valid arrangement has 0 in every cell strictly above the main diagonal. Return the fewest row swaps needed,or -1 when impossible. Column order cannot change.
```cpp
class Solution {
public:
int minSwaps(vector<vector<int>>& grid);
};
```
### Examples
**Example 1:**
```text
Input: grid = [[0,1],[1,0]]
Output: 1
Explanation: Swap the two rows so the top-right cell is0.
```
**Example 2:**
```text
Input: grid = [[1,1],[1,1]]
Output: -1
Explanation: Neither row has a trailing zero for the first position.
```
### Constraints
- grid is n by n,with `1 <= n <= 200`.
- Every grid entry is 0 or 1.
### Contract considerations
Rows may contain arbitrary binary patterns before their trailing-zero suffix.
```hint Read the boundary condition
Only adjacent row swaps are legal. Check every cell above the diagonal, all-zero rows, and arrangements that cannot be made valid.
```
### Boundary reminders
Rows may contain arbitrary binary patterns before their trailing-zero suffix.
Overview: Minimum Adjacent Row Swaps for Zeros Above the Diagonal. You may swap only neighboring rows of the square binary grid.
