[Leetcode 120, Medium] Triangle

Problem: 

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.

Analysis:

Solution:

C++:

int minimumTotal(vector<vector<int> > &triangle) 
    {
        if(triangle.size() == 0)
            return 0;

        vector<int> tempSumVec = triangle[triangle.size() - 1];
        for(int row = triangle.size() - 2; row >= 0; --row) {
            for(int col = 0; col < triangle[row].size(); ++col) {
                int leftSum = triangle[row][col] + tempSumVec[col];
                int rightSum = triangle[row][col] + tempSumVec[col + 1];
                if(leftSum < rightSum)
                    tempSumVec[col] = leftSum;
                else
                    tempSumVec[col] = rightSum;
            }
            tempSumVec.erase(tempSumVec.end() - 1);
        }
        
        return tempSumVec[0];
    }

Java:

Python: