I have seen this question on https://www.***.com/problem/shortest-path-in-matrix/description.
But since there is no solution and nearly no discussion, I hope I can see more brilliant ideas here on Leetcode.

Problem description:
Given the matrix of M rows and N columns, 0 represents empty space,- 1 represents obstacle, and 1 represents target points (there are multiple target points).

For each empty space, if you want to reach a target point at the shortest distance, please mark the direction of the first step.

If starting up, you should mark the point as 2. if starting down , you should mark the point as 3. if starting left , you should mark the point as 4. if starting right , you should mark the point as 5.

The priority of direction is up, down, left and right from big to small, that is, if you can reach the target point with the shortest distance from a point up or down, you are supposed to start up.

Returns the matrix after marking.
0<m,n<1000

My sub-optimal thought is, from each target, searching the path to each empty cell using BFS, while update its last step direction(which in reverse is the direction of first step from empty cell). We maintain the distance and corresponding direction of each cell. This method is TLE.