Find the Length of a Longest Path in a Manhattan-like Grid solved by 901

Length of a Longest Path in the Manhattan Tourist Problem

Find the length of a longest path in a rectangular city.

Given: Integers n and m, followed by an n × (m+1) matrix Down and an (n+1) × m matrix Right. The two matrices are separated by the "-" symbol.

Return: The length of a longest path from source (0, 0) to sink (n, m) in the n × m rectangular grid whose edges are defined by the matrices Down and Right.

Sample Dataset

4 4
1 0 2 4 3
4 6 5 2 1
4 4 5 2 1
5 6 8 5 3
-
3 2 4 0
3 2 4 2
0 7 3 3
3 3 0 2
1 3 2 2

Sample Output

34