LeetCode #113 Path Sum II

Medium

Problem

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

Note: A leaf is a node with no children.

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]
]

Solution

Use recursively DFS for searching matching path.

Complexity

Because each node will be iterated once, it takes O(n) time if n denotes to counts of nodes in this tree.

For space complexity, the calls in calling stack may reach h if h denotes to the length of the deepest path in the tree. So it’s space complexity is O(h). Or you can say O(logn) because h is bounded by logn.