leetcode1305 All Elements in Two Binary Search Trees

 """
 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]
 """
 class TreeNode:
     def __init__(self, x):
         self.val = x
         self.left = None
         self.right = None

 """
 此题提供三种思路，与leetcode98类似，https://www.cnblogs.com/yawenw/p/12376942.html
 第一种是层次遍历，
 然后对存入的值sorted排序
 传送门:https://blog.csdn.net/qq_17550379/article/details/103838538
 """
 class Solution1:
     def getAllElements(self, root1, root2):
         q, res = [root1, root2], []
         while q:
             cur = q.pop(0)
             if cur:
                 res.append(cur.val)
                 if cur.left != None:
                     q.append(cur.left)
                 if cur.right != None:
                     q.append(cur.right)
         return sorted(res)

 """
 第二种是利用二叉搜索树的条件，
 对两个树分别中序遍历。这样两个list分别有序
 再进行归并排序
 """
 class Solution2:
     def getAllElements(self, root1, root2):
         q1, q2 = [], []
         res = []
         # 中序遍历
         def inorder(root, q):
             if root:
                 inorder(root.left, q)
                 q.append(root.val)
                 inorder(root.right, q)
         inorder(root1, q1)
         inorder(root2, q2)
         # 归并排序的方法
         while q1 or q2:
             if not q1:
                 res += q2
                 break
             if not q2:
                 res += q1
                 break
             else:
                 res.append(q1.pop(0) if q1[0] < q2[0] else q2.pop(0))
         return res

 """
 第三种是：
 先中序遍历(代替层次遍历)
 再sorted(代替归并排序)
 """
 class Solution3:
     def getAllElements(self, root1, root2):
         res = []
         def inOrder(root):
             if root:    #!!!bug 没有写次if语句
                 inOrder(root.left)
                 res.append(root.val)
                 inOrder(root.right)
         inOrder(root1)
         inOrder(root2)
         return sorted(res)