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.
PathSumII

Given a binary tree and a sum, find all root-to-leaf paths where each
path's sum equals the given sum.

For example:
Given the below binary tree and sum = 22,
              5
             / \
            4   8
           /   / \
          11  13  4
         /  \    / \
        7    2  5   1
return
[
   [5,4,11,2],
   [5,8,4,5]
]