Lattice fetch number problem

Title Details: There are n*n, each lattice has a positive number or 0, from the top left corner to the bottom right corner, can only
Down and to the right, a total of two times (that is, from the upper left to the lower right corner to walk two times), the number of all the past lattice added up,
The maximum sum is calculated and two times if the same lattice is passed, the count of the lattice in the last sum sum is only added once. method One:

Refer to Chapter 34 of the Art of programming
Time complexity is O (n^3)
http://blog.csdn.net/rowanhaoa/article/details/15816067
It's called a two-thread dynamic programming problem , and it feels like a good idea. Method Two:

Http://www.360doc.com/content/13/1127/17/14357424_332618655.shtml
This method of time complexity is O (n^4), although slightly worse, but easy to understand