[Leetcode] Binary Tree Paths

Problem

Given a binary tree, return all root-to-leaf paths.

For example, given the following binary tree:

   1
 /   \
2     3
 \
  5

All root-to-leaf paths are:

["1->2->5", "1->3"]

Analysis

• Recursive constructing the path in bottom up fashion
• For each node, get its left and right paths recursively, denote them as left and right, then the recursion is
•  (node.val + (each path in left))
• (node.val + (each path in right))
• Time: O(N) where N is the number of nodes in the tree

Code