题解 | #合并二叉树#

class Solution:
    def mergeTrees(self , t1: TreeNode, t2: TreeNode) -> TreeNode:
        # 一颗子树为空，返回另一颗子树
        if not t1: return t2
        if not t2: return t1
        # 两棵子树均不为空，当前节点值相加
        t1.val += t2.val
        # 递归左子树
        self.mergeTrees(t1.left, t2.left)
        # 如果t1左子树不存在，则把t2左子树给t1
        if not t1.left:
            t1.left = t2.left
        # 递归左子树
        self.mergeTrees(t1.right, t2.right)
        # 如果t1右子树不存在，则把t2右子树给t1
        if not t1.right:
            t1.right = t2.right
        return t1