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
[ , [3,4], [6,5,7], [4,1,8,3] ]
The minimum path sum from top to bottom is
2 + 3 + 5 + 1 = 11).
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.
NOTE: You only need to implement the given function. Do not read input, instead use the arguments to the function. Do not print the output, instead return values as specified. Still have a question? Checkout Sample Codes for more details.