leetcode——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.

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

	}
};