Path Sum
Created: October 12, 2019 by [lek-tin]
Last updated: October 12, 2019
Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path 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 1
return true, as there exist a root-to-leaf path 5->4->11->2 which sum is 22.
Solution
python DFS
# Definition for a binary tree node.
# class TreeNode:
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
class Solution:
def hasPathSum(self, root: TreeNode, sum: int) -> bool:
return self.helper(root, 0, sum)
def helper(self, root, currSum, targetSum):
if not root:
return False
currSum += root.val
if not root.left and not root.right:
return currSum == targetSum
return self.helper(root.left, currSum, targetSum) or self.helper(root.right, currSum, targetSum)