Path Sum II

Problem: Path Sum II

We can do depth-first search on the whole tree and once we get a root-to-leaf path sum to target, we append the path to the results.

Code in Python:

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution(object):
    def pathSum(self, root, sum):
        """
        :type root: TreeNode
        :type sum: int
        :rtype: List[List[int]]
        """
        if not root: return []
        ans = []
        def dfs(node, _sum, path):
            if not node.left and not node.right:
                if _sum+node.val == sum: ans.append(path+[node.val])
            if node.left: dfs(node.left, _sum+node.val, path+[node.val])
            if node.right: dfs(node.right, _sum+node.val, path+[node.val])
        dfs(root, 0, [])
        return ans