题解 | #合并二叉树#

题目中是对两颗二叉树的每个结点进行值得合并，最终返回根节点，则以根节点开始，从上至下递归得出每个结点的左子结点和右子结点的值即可
代码：

class Solution:
    def mergeTrees(self , t1 , t2 ):
        # write code here
        if not t1 and not t2:
            return None
        if not t1 and t2:
            root = TreeNode(t2.val)
            root.left = self.mergeTrees(None, t2.left)
            root.right = self.mergeTrees(None, t2.right)
        if t1 and not t2:
            root = TreeNode(t1.val)
            root.left = self.mergeTrees(t1.left, None)
            root.right = self.mergeTrees(t1.right, None)
        elif t1 and t2:
            root = TreeNode(t1.val +t2.val)
            root.left = self.mergeTrees(t1.left, t2.left)    
            root.right = self.mergeTrees(t1.right, t2.right)
        return root