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.

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