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.

class Solution {
public:
    int minimumTotal(vector<vector<int> > &triangle) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        vector<int> r(triangle.back());
        for(int ii = triangle.size()-2; ii >= 0; --ii){//row
            for(int jj = 0; jj <= ii; ++jj){//col
                triangle[ii][jj] += min(triangle[ii+1][jj], triangle[ii+1][jj+1]);
            }
        }
        return triangle[0][0];
    }
};