Triangle.java

TriangleOct 30 '12
Given a triangle, find the minimum path sum from top to bottom. Each step you may move to adjacent numbers on the row below.

For example, given the following triangle
[
     [2],
    [3,4],
   [6,5,7],
  [4,1,8,3]
]
The minimum path sum from top to bottom is 11 (i.e., 2 + 3 + 5 + 1 = 11).

Note:
Bonus point if you are able to do this using only O(n) extra space, where n is the total number of rows in the triangle.

public class Solution {
	public int minimumTotal(ArrayList<ArrayList<Integer>> triangle) {
	int n = triangle.size() - 1;
        int[] path = new int[triangle.size()];
        for (int o = 0; o < triangle.get(n).size(); o++) {
            path[o] = triangle.get(n).get(o);
        }
        for (int i = triangle.size() - 2; i >= 0; i--) {
            for (int j = 0, t = 0; j < triangle.get(i + 1).size() - 1; j++, t++) {
        	path[t] = triangle.get(i).get(t) + Math.min(path[j], path[j + 1]);
            }
        }
        return path[0];
    }
}