leetcode979

搞不定这种递归计算，可能我的头脑是“线性”的，这种一层一层的，想起来太费劲了，想的头发都没了。以后希望能有AI来写这种程序吧，AI不怕掉头发！

 class Solution(object):
     def __init__(self):
         self.res = 0

     def dfs(self,root):
         if not root:
             return 0
         left = self.dfs(root.left)
         right = self.dfs(root.right)
         self.res += abs(left) + abs(right)
         return root.val + left + right - 1

     def distributeCoins(self, root: TreeNode) -> int:
         self.dfs(root)
         return self.res

参考：https://leetcode.com/problems/distribute-coins-in-binary-tree/discuss/221930/JavaC%2B%2BPython-Recursive-Solution