Triangle

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]
]

he 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.

Java

public class Solution {
    public int minimumTotal(List<List<Integer>> triangle) {
        int row = triangle.size();
        if(row == 0) {
            return 0;
        }

        int[] sum = new int[triangle.get(row - 1).size()];

        for(int i = row - 1; i >=0; i--) {
            for(int j = 0; j < triangle.get(i).size(); j++) {
                if(i == row - 1) {
                    sum[j] = triangle.get(i).get(j);
                } else {
                    sum[j] = Math.min(sum[j], sum[j + 1]) + triangle.get(i).get(j);
                }
            }
        }
        return sum[0];
    }
}