Given a square grid of integers arr, a falling path with
non-zero shifts is a choice of exactly one element from each row of
arr, such that no two elements chosen in adjacent rows are in the same
column.
Return the minimum sum of a falling path with non-zero shifts.
Example 1:
Input: arr = [[1,2,3],[4,5,6],[7,8,9]] Output: 13 Explanation: The possible falling paths are: [1,5,9], [1,5,7], [1,6,7], [1,6,8], [2,4,8], [2,4,9], [2,6,7], [2,6,8], [3,4,8], [3,4,9], [3,5,7], [3,5,9] The falling path with the smallest sum is [1,5,7], so the answer is 13.
Constraints:
1 <= arr.length == arr[i].length <= 200-99 <= arr[i][j] <= 99