Path Sum - LeetCode

Path Sum - LeetCode

题目：

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.

分析：

就是一个简单的递归计算来判断。

代码：

class Solution:
    # @param root, a tree node
    # @param sum, an integer
    # @return a boolean
    def hasPathSum(self, root, sum):
            return self.bfs(root,0,sum)

    
    def bfs(self,root,v,sum):
        if not root:
            return False
        if root.left == None and root.right == None:
            return v+root.val == sum
        return self.bfs(root.left,v+root.val,sum) or self.bfs(root.right,v+root.val,sum)