leetcode1305

class Solution:
    def midOrder(self,root,l):
        if root != None:
            if root.left != None:
                self.midOrder(root.left,l)
            l.append(root.val)
            if root.right != None:
                self.midOrder(root.right,l)
                
    def getAllElements(self, root1: TreeNode, root2: TreeNode) -> List[int]:
        l1,l2 = [],[]
        self.midOrder(root1,l1)
        self.midOrder(root2,l2)
        res = []
        n1,n2 = len(l1),len(l2)
        i,j = 0,0
        while i < n1 and j < n2:
            if l1[i] <= l2[j]:
                res.append(l1[i])
                i += 1
            else:
                res.append(l2[j])
                j += 1
        if i < n1:
            res += l1[i:]
        elif j < n2:
            res += l2[j:]
        return res

分别使用中序遍历两颗二叉搜索树，得到两个有序列表。再将两个数组合并为一个有序数组。