Triangle

Description:

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.

Code:

  int minimumTotal(vector<vector<int> > &triangle) {
        //注意三角形的存储顺序，顶端是第一行数据
        if (triangle.empty())
            return 0;
        int row = triangle.size();
        
        vector<int>nextRow(triangle[row-1]);
        vector<int>currentRow;
        for (int i = row-2; i >= 0; --i)
        {
            int col = triangle[i].size();
            currentRow = triangle[i];
            for (int j = 0; j < col; ++j)
            {
                currentRow[j] += min(nextRow[j], nextRow[j+1]);
            }
            nextRow = currentRow;
        }
        return nextRow[0];
    }