120. Triangle

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] ]

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.

Solution

public class Solution {


    public int minimumTotal(List<List<Integer>> triangle) {
        List<Integer> result = triangle.get(triangle.size() - 1);

        for (int i = triangle.size() - 2; i >= 0; i--) {
            for (int j = 0; j <= i; j++) {
                result.set(j, Math.min(result.get(j), result.get(j+1)) + triangle.get(i).get(j));
            }
        }

        return result.get(0);
    }
}