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[leetcode] path sum @ Python [recursion]
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.
For 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.
思路： 递归的暴力破解。
穷尽式的解决了所有子问题后，就放心的自我调用吧。
# Definition for a binary tree node# class TreeNode:# def __init__(self, x):# self.val = x# self.left = None# self.right = Noneclass Solution: # @param root, a tree node # @param sum, an integer # @return a boolean def hasPathSum(self, root, sum): if root == None: return False if root.val == sum and root.left == None and root.right == None: return True return self.hasPathSum(root.left, sum - root.val) or self.hasPathSum(root.right, sum - root.val)
[leetcode] path sum @ Python [recursion]
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