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, wheren is the total number of rows in the triangle.

class Solution {
public:
    int minimumTotal(vector<vector<int> > &triangle) {
       int i,j;
	   for(i=triangle.size()-2;i>=0;i--)
	   {
	      for(j=0;j<i+1;j++)
			  triangle[i][j]=min(triangle[i+1][j],triangle[i+1][j+1]);
	   
	   }
	   return triangle[0][0];

    }
};