You are given a grid, where each cell, grid[i][j], can have one of the following values:
1 indicates the starting point. There is exactly one such square.
2 marks the ending point. There is exactly one such square.
0 represents empty squares that can be walked over.
-1 represents obstacles that cannot be crossed.
Your task is to return the total number of unique four-directional paths from the starting square (1) to the ending square (2), such that every empty square is visited exactly once during the walk.
Constraints:
grid.length
grid[i].length
You are given a grid, where each cell, grid[i][j], can have one of the following values:
1 indicates the starting point. There is exactly one such square.
2 marks the ending point. There is exactly one such square.
0 represents empty squares that can be walked over.
-1 represents obstacles that cannot be crossed.
Your task is to return the total number of unique four-directional paths from the starting square (1) to the ending square (2), such that every empty square is visited exactly once during the walk.
Constraints:
grid.length
grid[i].length