python递归
class Solution:
def hasPathSum(self , root: TreeNode, sum: int) -> bool:
# write code here
if not root: return False
elif not root.left and not root.right:
return True if root.val==sum else False
else:
return self.hasPathSum(root.left,sum-root.val) or self.hasPathSum(root.right,sum-root.val)