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).

public class Solution {
    public int minimumTotal(ArrayList<ArrayList<Integer>> triangle) {
        int row = triangle.size();
        if(row<=0) return 0;
        int num[] = new int [triangle.get(row-1).size()];
        for(int i=row-1;i>=0;i--){
            int size = triangle.get(i).size();
            for(int j=0;j<size;j++){
                if(i==row-1)
                    num[j] = triangle.get(i).get(j);
                else{
                    num[j] = Math.min(num[j],num[j+1])+ triangle.get(i).get(j);
                }
            }
        }
        return num[0];
    }
}