题目
Given two binary search trees root1 and root2.
Return a list containing all the integers from both trees sorted in ascending order.
Example 1:
Input: root1 = [2,1,4], root2 = [1,0,3]
Output: [0,1,1,2,3,4]Example 2:
Input: root1 = [0,-10,10], root2 = [5,1,7,0,2]
Output: [-10,0,0,1,2,5,7,10] Example 3:
Input: root1 = [], root2 = [5,1,7,0,2]
Output: [0,1,2,5,7] Example 4:
Input: root1 = [0,-10,10], root2 = []
Output: [-10,0,10] Example 5:
Input: root1 = [1,null,8], root2 = [8,1]
Output: [1,1,8,8] 最直观的想法是先做遍历，然后得到两个有序的array，然后进行插入排序。
这样的话整体的复杂度就是O(M+N)，比如要做两次，有办法优化吗？