README.md

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.

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]
]

Solutions (Python)

1. Solution

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def pathSum(self, root: TreeNode, sum: int) -> List[List[int]]:
        if not root:
            return []

        if not (root.left or root.right) and root.val == sum:
            return [[root.val]]

        paths = self.pathSum(root.left, sum - root.val)
        paths.extend(self.pathSum(root.right, sum - root.val))

        for path in paths:
            path.insert(0, root.val)

        return paths