120. 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.

---

 

public class Solution {
    public int minimumTotal(ArrayList<ArrayList<Integer>> triangle) {
    
         int n = triangle.size();
         int[] p = new int[n+1];
         
         while(n > 0){
             n--;
             for(int i=0; i<=n; i++){
                 p[i] = triangle.get(n).get(i) + (p[i]<p[i+1] ? p[i] : p[i+1]);
             }
         }
         
         return p[0];
    }
}