#637 · #1368 · Minimum Cost to Make at Least One Valid Path in a Grid(使网格图至少有一条有效路径的最小代价)

You are given an m x n grid where each cell holds an arrow direction (1 = right, 2 = left, 3 = down, 4 = up). You may modify any cell's arrow at cost 1. Return the minimum cost to make at least one valid path from the top-left to the bottom-right. Constraints: 1 <= m, n <= 100.