1706. Where Will the Ball Fall - LeetCode

class Solution:
    def findBall(self, grid: list[list[int]]) -> list[int]:
        N = len(grid[0])

        def drop(pos: int) -> int:
            for row in grid:
                adj = pos + row[pos]
                if not 0 <= adj < N:
                    return -1
                if row[pos] != row[adj]:
                    return -1
                pos = adj
            return pos

        return [drop(x) for x in range(N)]