112. 路徑總和

class Solution:
    def hasPathSum(self, root, sum):
        """
        :type root: TreeNode
        :type sum: int
        :rtype: bool
        """
        if root is None:
            return False
        if root.left == None and root.right == None:
            return sum == root.val
        elif root.left == None and root.right != None:
            return self.hasPathSum(root.right, sum-root.val)
        elif root.left != None and root.right == None:
            return self.hasPathSum(root.left, sum-root.val)
        else:
            return self.hasPathSum(root.left, sum-root.val) or self.hasPathSum(root.right, sum-root.val)