### 113. Path Sum II

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]
]


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