Description
- Mario is in a maze, please help Mario to find max available number of coins at the Nth step,
- There are four direction(up, down, left, right) he can move.
- You can not go back.
- ex: N=2, It can not be considered as 1(first step at (1, 4)) -> 9(second step at (2, 4))
- Hint: Level-order tree traversal
Input
- Zero means wall.
Output
