------
## 最终结论
```python
def minPath(grid, k):
    from itertools import product

    N = len(grid)
    directions = [(0, 1), (1, 0), (0, -1), (-1, 0)]

    def neighbors(r, c):
        for dr, dc in directions:
            nr, nc = r + dr, c + dc
            if 0 <= nr < N and 0 <= nc < N:
                yield nr, nc

    min_path = None

    def dfs(path, r, c):
        nonlocal min_path
        if len(path) == k:
            if min_path is None or path < min_path:
                min_path = list(path)
            return

        for nr, nc in neighbors(r, c):
            dfs(path + [grid[nr][nc]], nr, nc)

    # Try starting from each cell in the grid
    for r, c in product(range(N), range(N)):
        dfs([grid[r][c]], r, c)

    return min_path
```