Project Euler: Problem 67 – Maximum path sum II

Problem 67:

By starting at the top of the triangle below and moving to adjacent numbers on the row below, the maximum total from top to bottom is 23.

7 4
2 4 6
8 5 9 3

That is, 3 + 7 + 4 + 9 = 23.
Find the maximum total from top to bottom in triangle.txt (right click and ‘Save Link/Target As…’), a 15K text file containing a triangle with one-hundred rows.
NOTE: This is a much more difficult version of Problem 18 (and my attempt). It is not possible to try every route to solve this problem, as there are 299altogether! If you could check one trillion (1012) routes every second it would take over twenty billion years to check them all. There is an efficient algorithm to solve it. ;o)


Since I already did the work for this on problem 18, I decided to just do what I did for that problem, and sure enough, it worked rather quickly. On my computer, less than a second.

int answer = -1;

int[][] tree = EulerUtils.readMatrix("Problem_67.txt");
long start = System.currentTimeMillis();
EulerUtils.SumTreePath path = EulerUtils.treePath(tree,true);
long end = System.currentTimeMillis();
System.out.println("Start: "+start+"\tEnd: "+end);
answer = path.getSum();